Giuseppe Iurato
email: giuseppe.iurato@unipa.it

Two simple questions regarding cultural anthropology

Keywords: OEdipus complex, romantic and maternal love, neurobiology, racism, Rank birth's trauma

Taking into account some notable recent neuroimaging researches, the first question we treat is a simple consideration of psychoanalytic anthropology which would suggest the existence of possible neurological bases to that fundamental psychoanalytic assumption which is the Freudian OEdipus complex. In such a manner, this first question so argued, is a very brief sketch which has been just thought simply to highlight this multidisciplinary interconnection that, among other things, gives a further corroboration of some chief principles of structural anthropology according to Lévi-Strauss. The second and final question, instead, deals with racism, trying to identify its early motivations and deep roots in the unconscious traces ontophylogenetically left by the so-called Rank's trauma of birth.

First question: on the OEdipus complex in social anthropology

This very brief note is concerned with some remarkable recent neurological researches, namely the works [START_REF] Bartels | The neural basis of romantic love[END_REF], [START_REF] Bartels | The neural correlates of maternal and romantic love[END_REF], [START_REF] Zeki | The neurobiology of love[END_REF], which are centered on the possible neural correlates of maternal and romantic love. These might turn out to be of usefulness if one wished to find, within an interdisciplinary context, a neurobiological corroboration of one of the central pillars of the whole psychoanalytic framework, according to the classical Freudian trend. The OEdipus complex is the key point upon which to build up the whole orthodox psychoanalytic edifice. So, starting from these simple premises, our main intention would be oriented toward the search for a possible neurological basis to the well-known OEdipus complex in the Freudian sense, at least for child boys. We shall compare maternal and romantic love, identifying some overlapping zones. What will emerge, may be also thought as a corroboration of some of the main principles of structural anthropology according to Claude Lévi-Strauss, namely the one putting OEdipus complex at the early founding basis of society, whose (unconscious) structure arises with the crucial passage from nature to culture [START_REF] Iurato | Some Comments on the Historical Role of Fetishism in Economic Anthropology[END_REF].

The OEdipus complex is besides of fundamental importance for the whole psychic life pathway of every human being. Indeed, according to the authors of these researches 1 , «[…] the tender intimacy and selflessness of a mother's love for her infant occupies a unique and exalted position in human conduct. Like romantic love, to which it is closely linked, it provides one of the most powerful motivations for human action, and has been celebrated throughout the agesin literature, art and musicas one of the most beautiful and inspiring manifestations of human behaviour. It has also been the subject of many psychological studies that have searched into the long-lasting and pervasive influence of this love (or its absence) on the development and future mental constitution of a child […]. Yet little is known of brain areas and pathways that correlate with this extraordinary affective state in the human. In pursuing our studies of the neurological foundations of love [START_REF] Bartels | The neural basis of romantic love[END_REF], we therefore thought it worthwhile to turn our attention next to maternal love».

Therefore, there exists a strict correlation between the maternal love and the next romantic love phase, highlighting the extreme importance of the former in the latter, from a psychic standpoint. Going on again with the words of these authors, «[…] Maternal and romantic love share a common and crucial evolutionary purpose, namely the maintenance and perpetuation of the species. Both ensure the formation of firm bonds between individuals, by making this behaviour a rewarding experience. They therefore share a similar evolutionary origin and serve a similar biological function. It is likely that they also share at least a core of common neural mechanisms. Neuroendocrine, cellular and behavioural studies of various mammalian species ranging from rodents to primates show that the neurohormones vasopressin and oxytocin are involved in the formation and maintenance of attachment between individuals, and suggest a tight coupling between attachment processes and the neural systems for reward […]. This is confirmed by lesion, gene expression and behavioural studies in mammals […]. Interestingly, the same neurohormones are involved in the attachment between mother and child (in both directions) and in the long-term pair bonding between adults, although each neurohormone may have distinct binding sites and may be gender specific […]. Such similarities, as well as the obvious differences between the two kinds of love, lead one to expect a neural architecture that differs between the two modes of love in some respects and yet is identical in others».

Thus, the authors have identified common neurobiological zones between neural architectures of these two chief types of love which are at the early bases for the perpetuation of human life, allowing the reciprocal exogamic coupling between humans, in coherence with the well-known Lévi-Strauss structuralism principles on the crucial passage from nature to culture.

The research authors, Bartels and Zeki, after a long and in-depth neurological discussion of their valuable experimental results, conclude, in [START_REF] Bartels | The neural correlates of maternal and romantic love[END_REF], saying as follows.

«This study complements our earlier one [START_REF] Bartels | The neural basis of romantic love[END_REF] and shows that (i) romantic and maternal love both involve a unique and overlapping set of areas, as well as areas that are specific to each; (ii) the activated regions belong to the reward system and are also known to contain a high density of receptors for oxytocin and vasopressin, suggesting that the neurohormonal control of these strong forms of attachment observed in animals also applies to the human; (iii) both forms of attachment suppressed activity in regions associated with negative emotions, as well as regions associated with 'mentalizing' and social judgment. This suggests that strong emotional ties to another person inhibit not only negative emotions but also affect the network involved in making social judgments about that person. Overall, the results lead us to conclude that attachment processes employ a push-pull mechanism that activates a specific pathway of the reward system of the brain. At the same time, circuits that are responsible for critical social assessment and for negative emotions are deactivated».

Hence, the authors point out too what next relevant social role play the numerous and important ties between maternal and romantic love, in establishing or not social relationships as well as in performing emotional states, according to the gender identifications built up in the childhood inside the given familial environment. Then, the authors insist again on the potentialities regarding the interrelationship sphere of every human being, stating that «Both studies on maternal and romantic attachment revealed activity that was not only overlapping to a large extent with each other, but also with the reward circuitry of the human brain […]. In summary, our findings show that both romantic and maternal love activate specific regions in the reward system, and lead to suppression of activity in the neural machineries associated with the critical social assessment of other people and with negative emotions. Since surprisingly, little is known about social processing in the human brain, we should emphasize that the following interpretations are of a rather tentative nature. There is no doubt that future studies will address these points more explicitly».

All this confirms as well, as said above, some of the main statements of Lévi-Strauss structuralism principles, besides originally worked out just referring to Freudian ideas. In this regard, the authors hope new studies spring out along this direction, advocating the consideration of social models just based on the tie provided by the emotional interaction established by this intertwinement between maternal and romantic love, stating that «Nevertheless, a potential model may be that once one is closely familiar with a person (in a positive or negative way), the need to assess the social validity of that person is reduced. This correlates with a reduction of activity in the systems necessary for doing so; these findings therefore bring us closer to explaining in neurological terms why 'love makes blind'. The neural mechanisms suppressed here might be the same that, when active, are responsible for maintaining an emotional barrier towards less familiar people, corresponding to the avoidance behaviour observed both in rats and in voles against pups or potential partners, which is reversed by administration of oxytocin […]. Our findings of consistently activated and deactivated regions with attachment may be indicative a fine balance between activity states of these regions that needs to be maintained to ensure a healthy social interaction. This may be important for the understanding of the severe psychological and clinical consequences that ensue when elements of this circuitry are interrupted, through inheritance, lesion or upbringing […]. The link of activated brain sites to the well-studied neurohormones, oxytocin and vasopressin and their binding sites offers a surprisingly straightforward way for pharmacological intervention that could be used both to induce and maybe more importantly to suppress feelings of attachment, as it has been successfully done in animals […]. On the whole, our results suggest a push-pull mechanism of attachment, that on one hand deactivates areas mediating negative emotions, avoidance behaviour and social assessment, and on the other triggers mechanisms involved in reward. These results have thus brought us a little, but not much, closer to understanding the neural basis of one of the most formidable instruments of evolution, which makes the procreation of the species and its maintenance a deeply rewarding and pleasurable experience, and thereby ensures its survival and perpetuation».

Therefore, the recalls to the main points of the Freudian OEdipus complex, both in its positive and negative form (cf. [START_REF] Laplanche | The Language of Psycho-Analysis[END_REF] for the related psychoanalytic notions herein invoked), above all for boys, are manifestly foreshadowed by the conclusions of these type of neurological researches, like those achieved above all in [START_REF] Bartels | The neural correlates of maternal and romantic love[END_REF] and [START_REF] Zeki | The neurobiology of love[END_REF].

Second question: a psychoanalytic anthropology remark on racism

The great and severe problem of racism is yet old as mankind at least until up appeared the idea of human race that, according to the latest socio-anthropological researches, is devoid of any scientific basis, but it is only a mere, although ubiquitous, social-cultural phenomenon which should be better historically understood in its deep ethnographic roots. What truly makes difference between distinct human agreements, is only the social-cultural environment where them live. Notwithstanding that, in many countries explicit forms of racism have become increasingly a social taboo. Even in those people who manifestly display and claim egalitarian explicit attitudes, a sort of implicit racism is still maintained, unconsciously. Therefore, if one wishes to seek possible causes or reasons to this iniquitous social phenomenon, then a possible related outlook might be provided by psychoanalytic context, although just the psychodynamic trend was at once abandoned after some first studies made tomorrow Nazi tragedy, above all by German psychologists and social scientists like D. Katz, and some exponents of the Frankfurt school.

On the other hand, the so-called symbolic racism, which is maybe the most prevalent racial attitude today, has many implicit, or unconscious, aspects, as recently pointed out by [START_REF] Tarman | The Conceptualization and Measurement of Symbolic Racism[END_REF] and [START_REF] Whitley | The Psychology of Prejudice and Discrimination, 2nd Edition, Wadsworth Cengace Learning[END_REF], so that it seems quite obvious to think to adopt, yet again, a psychodynamic view, at least to try to explain some features of this social phenomenon. To be precise, we focalize on the main fact that, often, the social groups involved in this bad phenomenon have a particular position from a historicethnographic stance, in the sense that racism is often2 displayed toward that ethnicity having a longest phylogenetic origin along the crucial historical human migration movement pathway 3 , at least for those ethnicities which may be locally placed around this, or simply towards those people who geographically stay in southern zones 4 .

Then, if one looks at the unconscious features of this archaic and ubiquitous phenomenon, it would be possible to suppose that its early reasons might be ascribed to certain archetypical motifs of the collective unconscious. To be precise, we would like to put, at the basis of racism, a phylogenetic extension of the so-called trauma of birth, exposed by Otto Rank, and dating back to 1923 but published in a celebrated work of 1924, also on the basis of previous Freudian ideas. This trauma was introduced by Rank to basically explain a universal human experience, as the anguish, through another as many universal event, the birth, meant as a prototrauma. Following [START_REF] Fossi | Le teorie psicoanalitiche[END_REF], Rank claims that, during preuterine life, the foetus experiences a total and blissful union with the mother, a tie which will continue in the next life course as a seek for a complete fulfilment. But the birth breaks this condition of symbiotic beatitude in such a manner to become insomuch traumatic to be then, for the complete absence of Ego's defences, the prototype as well as the origin of every next anxiety due to the fear of separation, producing a kind of anxiety's reserve which will be re-enacted every time a separation's event occurs.

At the birth, the child is fully unable to acquire her or his own defence's system, so experiencing a heavy and overpowering set of stimuli against which he or she cannot build up any defence barrier. Thus, with the rising of corporal Ego experiences or feels, a so strong impotence sense, out of the control of the child, springs out in such a manner that, the related response of the Ego in front of such an intense and immediate experience, is overwhelmed by anguish. Therefore, the desire to reestablish the blissful of pre-uterine condition, enters into a conflict with the remembrance of the birth's trauma, with a great related anxiety. This Rank's conception was accepted by Freud, notwithstanding the next breakdown between them, bringing back the anguish to this original trauma 5 . The birth is the only universal event of human life characterized by such a high, sudden, violent and drastic change either in the surrounding environment and in the physiological conditions in such a manner to make it a unique and singular event, also due to the imposingness of the obstetric material operation itself if one looks at the foetus dimensions. Such a singular traumatic experience will be variously symbolically relived in many other occasions of the life of an individual. Freud, therefore, considered Rank's viewpoint as valid only to enlarge his sight on anguish, regarding birth as the prototype of a fundamental and primary situation in which human being undergoes the higher stimulation both internal and external. When such a situation re-occurs each time the individual has neither any knowledge or fully awareness of it nor any capability to cope it with available, suitable defence or protective means, then a new traumatic situation re-appears but still characterized by a rapid excessive stimulation which releases a painful and terrifying discharge assuming the form of a severe primary anguish together a fear to be annihilated and overwhelmed. The situation which gives rise to such an uncontrolled anguish, is said to be a traumatic situation, and re-evokes or re-enacts a kind of ''conditioned reflection of the primordial anguish''.

Following [START_REF] Ellenberger | La scoperta dell'inconscio. Storia della psichiatria dinamica[END_REF], Rank's idea for which every human being tends unconsciously to return back to maternal womb, was considered by C. Moxor as an anticipation of the Freudian concept of death drive. Before Rank, Freud himself had already expressed the opinion that child anguish, as experienced during birth's labour pains, were the prototype of every next anguish, even if, afterwards, Freud rejected Rank's theory because threatened the pillar of his theory, that is to say, the OEdipus complex. On the other hand, as E. Glover noticed, some analysts, after Rank's work on birth's trauma, effectively discovered traces of this trauma in each of their patients. This fact, nevertheless, was neglected after that Rank's trauma of birth was officially repudiated by Freud. In any case, Freud himself, since early 1900s, encouraged his co-workers and pupils to turn towards the study of myths. Indeed, in the Rank's trauma of birth, just due to its universality and unavoidability 6 , it is also possible to descry archetypical features, also on the basis of the simple fact that Rank surely known Jung's work (cf. [START_REF] Carotenuto | Breve storia della psicoanalisi[END_REF]), so that such a trauma has surely an archetypical source as well. Indeed, as regard the pioneering Stanislaw Grof researches, in the words of Karen Pohn of the Antioch University at Los Angeles, «Grof's work with psychedelics yielded many interesting insights that led him, during the 1960s, to create a new expanded cartography of the psyche. Grof's Freudian training only took him so farwhile some of the experiences that people had during psychedelic sessions reflected biographical material from childhood, there were many other experiences that did not correspond to the Freudian personal unconscious. Some subjects had experiences that seemed to be archetypal in nature, and were not consciously known to the person and thus seemed to reflect Jung's notion of the collective unconscious. Still others had non-human experiences like becoming an eagle or a granite mountain, where they came away with insights that later were confirmed by research. Also, a significant number of people seemed to experience their own birth.

Otto Rank had previously written about the birth experience in his 1924 book The Trauma of Birth, which caused Rank's ousting by Freud, much as Jung's 1913 work Symbols of Transformation (Wandlungen und Symbole der Libido), […] had caused Jung's parting with Freud earlier. Indeed when Freud read Rank's book, Freud was severely shaken for several months because he felt that Rank's discovery was so important that it might eventually prove more important than Freud's own work. Freud had earlier suggested that the trauma of birth might indeed be the blueprint for all future anxiety, and Rank ran with this idea. Indeed Freud referred to Rank's book as ''the most important progress since the discovery of psychoanalysis''. Rank believed that all human mental life has its origin in the anxiety and repression of the birth experience, and that later traumatic events derive their power from this trauma. He saw that in childhood and later life we are constantly trying to master this trauma and that the birth trauma plays an important role in religion, art, and history. Rank also felt the birth trauma must be relived to effectively treat neurosis. Jung's Symbols of Transformation also contains material on the birth of the hero and death and rebirth motifs. These books that caused both Jung and Rank to split with Freud contained birth related motifs, proving birth to be a touchy subject.

[…] For Rank, the experience of paradise lost and the difference between the pre and post womb experience, was the trauma of birth, not the actual physical birth process itself. In other words, Rank felt that the trauma was in being expelled from the womb and being born, not the actual trauma that occurred as a result of the baby going through the rigors of labour. Rank felt that violence and weapon-making reflected a desire to get back into the womb, rather than focusing on the aggression that Grof associates with the passage through the birth canal. Grof's work elaborates and furthers Rank's work in that it concentrates on and articulates the importance of the actual physical stages of the birth process, which Rank did not consider.

Grof's expanded cartography of the psyche not only incorporated the Freudian personal unconscious, and the Jungian collective unconscious, but also the ''Rankian level'' that mirrored the birth process which Grof termed the perinatal level, meaning ''around birth''. This expanded cartography can be pictured as an hourglass with the personal unconscious at the bottom, the perinatal level at the meeting point of the two glasses and the collective/transpersonal unconscious, or archetypal level above, which includes but is not limited to Jung's notion of the collective unconscious, and is comprised of ancestral, racial, collective and phylogenetic memories, karmic experiences, and archetypal dynamics».

In conclusion, from what has just been said so far, above all with respect to the archetypical roots of birth's trauma, it does not seem at all unreasonable to try to identify possible early origins of racism in offshoots of the trauma of birth just deployed along the complicated and inextricable intertwined course involving ontogenesis and phylogenesis.

Each possible underscore of every quotation of original texts, is due only to me.

Of course, since we have to do with social phenomena, the case studies here considered not cover all the possible cases, but a certain though great number of them.

Which roughly has a two-branch structure given by two main geographical departure points, one placed around Atlantic coasts of central Africa, the other in Eurasia.

Or else, towards those people placed at lowest geographical latitudes, which implies a nearer proximity towards those terrestrial zones from which start the lines of early human migration.

See[START_REF] Musatti | Trattato di psicoanalisi[END_REF],[START_REF] Sias | Inventario di psicoanalisi[END_REF]. In[START_REF] Zetzel | Psichiatria psicoanalitica[END_REF], the authors say that Freud already known the main essence of the trauma of birth, before Rank.

See[START_REF] Cotsell | The Theater of Trauma. American Modernist Drama and the Psychological Struggle for the American Mind, 1900-1930[END_REF].


J Vercueil

Opening Russia? Contemporary foreign trade

Economic developments in Russia during the past two years have been fairly positive, compared to the earlier transition trajectory of the country. Belying most of the expectations, the mid-August crisis in 1998 has not resulted in a deepening of the output contraction. To the contrary, main macroeconomic performances of the Russian economy since 1999 have been impressive : economic growth has accelerated, reaching 7,7 per cent in 2000; after a peak linked to the monetary upheavals that had occurred immediately after the August crisis, inflation rate has progressively slowed down to about 20 per cent for the year 2000. Investment rate has also improved sharply, while industrial production accelerated its recovery.

The role of external factors in the Russian recovery is now widely recognised. This paper focuses on the design of commercial policy, in the broader context of external economic policy. Section I discusses whether the policy changes that have occurred in 1999 and 2000 can be seen as the progressive elaboration of a genuine economic strategy for the Russian external sector. Section II gives a preliminary assessment of the results registered so far in the external sector. Section III concludes briefly by recalling the main choices Russian government is going to face regarding commercial policy.

After the crisis : the progressive design of a strategy

Between 1998 and 2001, two major political shocks have changed the institutional environment of commercial policy. Firstly, the rouble devaluation and the partial default over the sovereign debt, in August and October 1998, have drastically altered the making of Russian economic policy. Secondly, the end of the so-called "Eltsine era", accompanied with new elections has made possible a partial reshuffling of the political heads of the State. This is not, by itself, a sufficient cause to a sudden move towards the design of a long-term economic strategy more favourable to Russia's economic and social interests, after six years of a missing strategy (Vercueil, 2001). But certain recent decisions of Russian authorities have shown a new tendency that is worth being explored.

Legislative (in December 1999) and Presidential (in March 2000) elections opened a new period of political stability that was more favourable to the progressive design of a genuine commercial policy. In the first "long term economic program" of the new Government, the target fixed to the mean import tariff was 15 to 16%, in line with the maximum levels usually accepted by IMF, World Bank and WTO. The tariff structure eventually adopted in the beginning of 2001 was based upon four main rates (5, 10, 15 and 20%), with higher rates for individual categories (cars, sugar, alcohol and tobacco). Nevertheless, a number of others restrictions are still being imposed on external trade and currency exchange : fuel exports are subject to a floating tax regime, depending on energy prices in world markets (Tchernavski, 2000), and exporting firms are required to sell 75% of their foreign currency earnings to the Russian market within 7 days after the sale. In the field of foreign investment, a clear breakthrough was obtained during 2000 by the progressive clarification of fiscal legislation, coming into force in January 2001. Several notorious disputes involving foreign investors were also settled during last year1 , strengthening the general improvement of investment climate in Russia. As a result, international rating agencies have progressively raised their evaluation of the Russian economy, while German and Finnish public export insurance companies resumed guaranteeing national exports to Russia2 . The last progress in this area was, in march 2001, the approval by the upper house of Parliament of an amendment to the Civil code allowing private property of non farm land 3 .

A topic of major interest in this context is the current process of WTO accession negotiations (Broadman, 1998). More than five years after the first official talks, it is now widely admitted that Russia has taken in 2000 decisive steps in the credibility of its accession process 4 . For Russia, economic incentives endeavour being better accepted by western commercial partners are clear : financial damages caused by various anti-dumping procedures and quotas imposed by European Union, on the basis of the classification of Russia as a nonmarket economy, are estimated at 2,5 bns $ a year. Canada, United States, South Korea and others countries are taking similar measures, that could be removed or, if not, discussed in a more comprehensive framework if Russian accession to WTO was completed. The latest Russian proposals were a little more liberal than previously announced in the long term economic program. They allow foreign investors to take bigger shares in service industries. Several structural laws are under preparation, aiming to bring Russian legislation closer to international rules in various areas (namely, intellectual property protection, State support for industries, customs regulations, commercial licensing, etc.). Nevertheless, recent statements from top level government officials tend to mean that Russia is willing to bargain strongly its accession. For instance, a five to seven years period of special status has already been asked for by Russian authorities, in order to enable domestic industries to face a more acute competition from outside. Among a wide range of topics, agricultural policy will be a subject of particular sensitiveness, given the political weight of the sector in Russia.

It is a bit early to assess the chances of Russia to become rapidly a full member of the WTO. But from an institutional point of view, the most important is to give confidence to economic agents, be they Russian or not, that the legal framework in which they conduct their activities can be stabilized et secured. Compared to the progress made in this area, it is of less importance to know whether Russian authorities have run as fast as possible in a so-called liberal direction.

Preliminary results : local strengths and global weakness of the Russian economy

Russian authorities may have been comforted in their strategy by some good news coming from the external sector: Russian trade balance posted a record surplus of 61 bns US $ in 2000, with an increase of the total value of export estimated at 39% over the year before, 3 thanks to the rapid rise in world fuel prices. The sharp devaluation of the rouble in fall 1998 provided an effective protection under which import-substitution became possible : in 1999, imports dropped by almost 30%, while industrial production increased by 8,1%; in 2000, the growth was even brisker (9%), with light industry showing the most spectacular recovery (+22%). For the whole year 2000, Russian enterprises declared 37-38 bns US $ of profit (most probably, a figure underestimated), of which more than 40% originated from the sole energy and metal sectors, two leading exporters in the Russian economy. Budget earnings also benefited from the windfall gains provided by the improved international position of Russia in 2000 : the largest increase was recorded in customs revenues, which soared as a share of total revenues from over 14% in 1999 to over 20% in 2000. Therefore, customs duties contributed largely to the impressive budget surplus recorded in 2000, totalling some 2.5% of GDP. In addition, one of the major weaknesses of Russian economy, the lack of investment, began to alleviate, thanks partly to the external sector : fixed investment totalled 42 bns US $, a 17% increase over previous year. Crude oil industries doubled their investments to a fifth of the total amount. On the other hand, metallurgy continued to lag behind (5% of the total investment), stagnating at the 1999 level. FDI represented 5% of the total registered this year, amounting to 4.4bn US $ -a 4% increase over the previous year-. Clearly, the role of external sector in the recovery of Russian economy was determinant in 1999-2000.

However, this picture is a bit too rosy to be complete. Several drawbacks inherited from the first years of transition are still far from being overcome :

First, the role of the energy sector in the restructuring of the Russian economy remains to be clearly defined by the authorities. The real appreciation of the rouble since 1999, due for the most part to export earnings from the energy sector, is beginning to impair the gradual recovery of others industrial sector : during the last quarter of 2000, imports have risen at an accelerated pace (20%), while exports began to slow down, as did domestic industrial output (+2,5% on a year-to-year basis in December). If this tendency were confirmed in 2001, hopes for an industrial diversification of export, much needed by the Russian economy [START_REF] Popov | Internationalisation of the Russian Economy : What Went Wrong[END_REF], could once again vanish.

Second, distorted incentives produced by the lack of a comprehensive policy cannot be abolished merely by the "dictatorship of the law". A practical illustration of this idea is the continuation of capital evasion in spite of the measures mentioned above and a continuous commitment of the authorities to fight against it [START_REF] Sicular | Capital Flight and Foreign Investment : Two Tales from China and Russia[END_REF], Westin, 2000). In 2000, capital flight rose again to an estimated amount of more than 20 bns US $, representing about ten percent of Russian GDP. At the same time, the value of foreign direct investment received by Russia was half the amount of Chile. This does not indicate that Russia is becoming an attractive country for genuine investors. Third, while institutional weaknesses that used to affect the Russian economy may have been less acute since the new administration clearly demonstrated its will to strengthen law implementation, a number of institutional issues regarding the external sector remain far from being solved. According to parliamentary estimations, more than 40 percent of private and some 60 percent of state-owned firms are now controlled by organized crime, with the figure in the banking sector reaching 85 percent. Most often, corruption is closely linked with international operations, since those activities provide earnings in hard currencies. In January 2001, the G-7' Financial Action Task Force (FATF) quoted Russia for the second time among the "non-cooperative jurisdictions" concerning legislative fight against money laundering. Economic negative consequences of corruption are not simply of an "efficiency" nature (even if the estimated cost of corruption in Russia is 15 bns US $) : the principal threat is that they undermine the credibility of the major institutions 5 of the country (the State, laws, conventions beween economic agents, etc.). The collective character of an institution is not recognised anymore when it becomes obvious that its initial purpose has been diverted for the profit of a minority. Under such conditions, the informational and stabilising role of the institution is no longer fulfilled; it leaves economic agents coping with an uncertain environment by striving to secure short term outcomes from their decisions. This logic of emergency brings many damages to the whole society, which begins to dislocate in various groups closed one to another. It also impairs normal wealth creation and economic development, as most of the resources are not used to invest in productive capacities, or to restructure and modernise economic organisations, but are simply dilapidated.

We have to add to this picture two others difficulties that Russia is bound to face in the near future :

The first one is linked with the most likely end of the exceptional window of opportunity enjoyed by Russia since the rouble devaluation : on the external side, the progressive strengthening of real exchange rate is likely to pursue, and world prices for energy have already declined, showing no clear tendency to recover soon. Given the dependency of both current account balance and budget earnings on the exports of fuel 6 , a sharp fall of energy prices could destabilise Russian international economic situation. On the internal side, there are many signs that the 'honeymoon' Russian government enjoyed with the State Douma has come to an end. Politically, it is likely to be more and more difficult to implement certain key reforms delayed until now, for instance in the banking sector.

The second one is the external debt burden, on which a partial default had been declared after the rouble devaluation. The domestic short term debt has been rapidly restructured in 1999, and an agreement has been reached over the longer term sovereign debt in 2000 with the London club, which represents foreign private creditors. However, this is not the case with the Paris club, which assembles public creditors to Russia. The beginning of year 2001 has shown the difficulties of the Government to cope with the problem, as well as the bargaining power of the Duma in such a strategic issue 7 . Meanwhile, Russian budget is still lacking the necessary funding for the repayment of other parts of its debt this year. Furthermore, the debt burden which is currently costing about 25% of the federal budget, is going to reach a peak in 2003. Last but not least, any restructuring agreement with the Paris Club requires a preliminary approval of an economic program by the IMF. So far, despite long and repeated talks, Russian officials have neither obtained nor accepted such an approval.

Conclusion : taking advantage of a favourable context.

5 In this paper, we see institutions as collective devices designed to produce and interpret rules of behaviour. 6 However, the budget projections for 2001 were calculated on the basis of a rather cautiously estimated fuel price of 21 US $ per barrel. 7 After official declarations threatening that Russia would not be able to pay its duty for the first quarter of 2001, bitter reactions of the main creditors -Germany and Italy -led to a u-turn in official attitudes and the full payment of the sum, thanks to an in-extremis agreement obtained by the Prime Minister with the Upper House of Parliament. .

As it has been shown, Russian commercial policy needs to be designed with due regard to the broader external economic policy. In order to achieve a consistent strategy, Russian authorities should bring together several types of policy :

1. An industrial policy, aiming at reducing scientific and technological backwardness in comparison with western countries, and at the same time encouraging spill-over from the energy and raw material sectors to others industries.

2. A capital account policy, managing in a comprehensive framework the various flows of capital -discouraging short term flows, and encouraging longer term ones -to dismantle the adverse selection effect currently affecting this sector 3. A debt settlement strategy, aiming to encourage debt-for-equity swaps with western creditors in order to alleviate the external burden on the budget and the modernisation of various domestic industrial sectors8 . From the point of view of international creditors, it could be of great interest to bargain a substantial discount on their controversial credit against stakes in some potentially valuable Russian enterprises.

These strategies require well-functioning banks to be fully implemented. For the time being, most of the financial sector's activity is concentrated in the management of public loans and the placement of major Russian enterprise earnings abroad. Banks accounted for only 2% of the financing of productive investment in 2000. Hence, one of current top priorities of the Government should be to implement the restructuring of Russian banks, enabling them to act as normal financial institutions.

At the same time, Russia will have to look carefully at its relationship with international organisations such as IMF, World Bank or WTO. Presently, Russia is in a position to choose whether to open or to close the door to international financing and complete access to world markets. But if its external situation were to deteriorate rapidly, it could force Russia to admit control conditions from abroad that are, for the moment, considered as politically unacceptable. That is why it is time for Russia to tackle actively the main problems discussed above, taking advantage from its current favourable situation to implement the necessary institutional and structural reforms, before the possible vanishing of the current window of opportunity.

For example, BP Amoco versus Sidanko and the lawsuit regarding the Lomonossov factory.

See Russian and Baltic Economies. The Week in Review. Bofit, n° 28,

31, 35, 40 (July-October 2000).3 It is interesting to note that, on the other hand, the possibility to own privately agricultural land has been postponed by the Sate Duma.4 See the assessment of WTO Director General Mike Moore : « Russia, the International Economy and the World Trade Organization »,Moscow, 30 March 2001.

Agreements have already been signed in March 2001, with German and Italian Counterpart, on an experimental scale.

6

Tchernavski C., 2000 : "Ob eksportnykh pochlinakh na neft", Expertny Ekonomitcheski Group Publication, n°2000/05. Vercueil J., 2001 : "La politique commerciale de la Russie (1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000). De la prédation à la reprise en main ?", Le Courrier des Pays de l 'Est, n°1012, pp. 4-19. Westin P., 2000 : "Export Revenues : Expatriation or Expropriation ?", Russian Economic Trends, Monthly Update, February, pp. 3-10.


Lourdes Diaz Olvera

Didier Plat
email: didier.plat@entpe.fr

Pascal Pochet
email: pascal.pochet@entpe.fr

Lourdes Diaz Olvera
email: lourdes.diaz-olvera@entpe.fr

data collection. Methodological issues and a case study (Douala, Cameroon)

Keywords: Household travel survey, income data collection, daily mobility, transport expenditure, mobility inequality, sub-Saharan Africa

de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

INTRODUCTION

In metropolitan areas that are experiencing marked spatial growth, as is the case in sub-Saharan Africa, access to the activities and resources afforded by the city is far from universal. This is primarily because of socio-geographical disparities in the distribution of urban services and jobs [START_REF] Myers | Disposable Cities: Garbage, Governance and Sustainable Development in Urban Africa[END_REF][START_REF] Rakodi | The urban challenge in Africa[END_REF]. However, the situation is further worsened by major inequalities in the use of motorised transport modes, not only cars but also public transport which is too expensive for poor city-dwellers to use on a regular basis [START_REF] Bryceson | Livelihoods, daily mobility and poverty in Sub-Saharan Africa[END_REF][START_REF] Diaz Olvera | The puzzle of mobility and access to the city in Sub-Saharan Africa[END_REF][START_REF] Lucas | Making the connections between transport disadvantage and the social exclusion of low income populations in the Tshwane Region of South Africa[END_REF][START_REF] Salon | Mobility, poverty, and gender: Travel "choices" of slum residents in Nairobi, Kenya[END_REF][START_REF] Sietchiping | Transport and mobility in sub-Saharan African cities: An overview of practices, lessons and options for improvements[END_REF].

Differences between individuals' travel behaviours obviously exist, in the same way that there are differences between their state of health and access to healthcare and, in the case of the young, their possibility of going to school. When such differences between individuals result in disadvantages with regard to daily mobility, they are perceived as inequalities if they are due to situations that are partially or completely unchosen (income, gender, age, physical capacities, accessibility of residential location, etc.). In sub-Saharan Africa, transport policies take little account of the issues of social and geographical equity, i.e. the goal of fostering a more equal access to mobility, and, more broadly, to urban resources.

Investments in urban transport are usually focused on the construction and maintenance of roads and benefit primarily the minority of citizens with private cars [START_REF] Vasconcellos | Urban Transport, Environment and Equity. The case for developing countries[END_REF]. The Bus Rapid Transit systems which have recently been built, or which are currently planned, in many large African cities (Addis Abeba, Dakar, Dar es Salaam, Lagos, etc.) could indicate a change of policy direction, but it is still too early to assess if they will be affordable and located where they can serve low income populations. Both these conditions must be satisfied if the mobility of the poor is to improve. [START_REF] Teunissen | Mapping Equality in Access: The Case of Bogotá's Sustainable Transportation Initiatives[END_REF] have shown, for example, in the case of Bogotá, that while the Transmilenio serves the zones with the greatest concentrations of poor people, its cost means they are unable to make much use of it. Such decisions on the part of the public authorities are explained by a variety of factors such as the role of international organisations and donors or the desire to have "modern" transport systems which use up-todate technology. But even if the public authorities wished to consider the impacts of transport policy with regard to equity, they would in most cases be unable to do so because of an absence of adequate statistical data. The knowledge of the scale and nature of intra-urban inequalities requires reliable statistics disaggregated by income group [START_REF] Mitlin | City inequality[END_REF]. Such income statistics must then be compared with travel behaviours. But as the investigation of travel issues is frequently concerned with engineering considerations, data collection is still very much focused on the travel of economically active groups [START_REF] Behrens | Collection of passenger travel data in Sub-Saharan African cities: Towards improving survey instruments and procedures[END_REF].

It is never straightforward to collect income data in household surveys, in particular because of refusals to respond and the fact that the amounts involved are, deliberately or not, inaccurately reported. Researchers have investigated this issue in countries of the North (see, in particular [START_REF] Davern | The effect of income question design in health surveys on family income, poverty and eligibility estimates[END_REF][START_REF] Hansen | Does how you measure income make a difference to measuring poverty? Evidence from the UK[END_REF][START_REF] Micklewright | How reliable are income data collected with a single question[END_REF][START_REF] Moore | Income measurement error in surveys: A review[END_REF][START_REF] Scott | Generating relevant household level data: Multi-topic household surveys[END_REF]. In the case of travel surveys in countries like the United States or Australia, [START_REF] Stopher | Collecting, Managing, and Assessing Data Using Sample Surveys[END_REF] recommends asking respondents to indicate a relatively wide income band rather than state the exact amount in order to reduce nonresponse rates. The issue of collecting income data in surveys has, however, been considerably less studied in developing countries, even though the estimation of income poses particularly great problems there [START_REF] Pettersen | Survey design and sample design in household budget surveys[END_REF][START_REF] Deaton | The analysis of household surveys: A microeconometric approach to development policy[END_REF][START_REF] Deaton | Consumption[END_REF]. In theory, a more satisfactory approach would be to evaluate the standard of living on the basis of household expenditure [START_REF] Deaton | Consumption[END_REF], but the complexity and cost of a protocol of this type means that it cannot be implemented in a household travel survey [START_REF] Diaz Olvera | Household transport expenditure in Sub-Saharan African cities: Measurement and analysis[END_REF]. The direct collection of individuals' incomes in these surveys is therefore indispensable. However, it raises three sets of difficulties, particularly in Africa.

First, several factors make it difficult to estimate the income derived from work. In this context where the amount of paid employment is falling and the number of informal microactivities is on the rise, many workers depend on precarious jobs and occasional work, for which they are paid irregular amounts at irregular times (De Vreyer and Roubaud, 2013). For the numerous self-employees, like petty traders or low-skilled craftpersons, it is difficult to estimate the net profit drawn from their activity as no accounts are kept. Similarly, in the case of young women, for example in apprenticeships, it is not at all easy to distinguish labour from domestic or nonremunerated activities. In addition, it is common for individuals to have a number of activities, and this applies not only to individuals in paid employment who do so in order to diversify their sources of income and to save, but also to individuals working in the informal sector, who do so in an attempt to compensate for the irregular nature of their principal activities [START_REF] Bocquier | Employment vulnerability and earnings in urban West Africa[END_REF][START_REF] Ersado | Income diversification in Zimbabwe: Welfare Implications from Urban and Rural Areas[END_REF][START_REF] Iyenda | Street enterprises, urban livelihoods and poverty in Kinshasa[END_REF].

Second, income cannot be restricted to the sums that are earned from professional activities. It also includes grants and benefits, rents, pensions and, above all, gifts from one individual to another. Particularly in the case of the latter, it is difficult to estimate the sums involved because of the irregular nature of the transfers. But even if chains of solidarity are tending to weaken [START_REF] Abdullah | Gender and Adjustment in Nigeria's Manufacturing Sector[END_REF]Leimdorfer and Marie, 2003;[START_REF] Séraphin | Vivre à Douala : L'imaginaire et l'action dans une ville africaine en crise[END_REF], gifts from outside the household continue to contribute significantly to the total income of individuals and households, particularly among the poor [START_REF] Lourenço-Lindell | Walking the Tight Rope: Informal Livelihoods and Social Networks in a West African City[END_REF].

Last, the economic behaviour of the population and the role of the household also add to the difficulty of estimating standards of living on the basis of income. Individuals are often unaware of the personal resources of the other members of their household, and not all income is pooled [START_REF] Glick | Schooling of girls and boys in a West African country: the effects of parental education, income, and household structure[END_REF][START_REF] Hoddinott | Does female income share influence household expenditures? Evidence from Côte d'Ivoire[END_REF][START_REF] Posel | Intra-family transfers and income-pooling[END_REF][START_REF] Yapi-Diahou | Baraques et pouvoirs dans l'agglomération abidjanaise[END_REF]. Among other things, the implication of this for transport is that access to motorised modes is more strongly conditioned by an individual's personal monetary resources than by those of his or her household [START_REF] Diaz Olvera | Household transport expenditure in Sub-Saharan African cities: Measurement and analysis[END_REF][START_REF] Venter | Gender, residential location, and household travel: Empirical findings from low-income urban settlements in Durban, South Africa[END_REF].

The aim of this paper is thus to evaluate in what way income data collection affects the accuracy of data and therefore the measurement of mobility inequalities. We have done this by referring to a household travel survey conducted in Douala (Cameroon) in 2003 in which respondents' income data was collected in a disaggregate and precise manner. The estimated values of mobility inequalities obtained from this survey have been compared with what was observed from less sophisticated data collection. This data was not the outcome of specific fieldwork conducted at the same time as the travel survey but was obtained from ex post simulations which provide less accurate income data, that are comparable with those obtained from surveys that collect income data in a much simpler way. The case study provides a variety of information about mobility inequalities in Douala. However, our aim is not to analyse their determinants or to identify policies that might reduce them, but rather to evaluate how their measurement is affected by a number of methodological decisions.

After a short description of the local context of Douala, Section 2 describes the income data collection procedure used for the travel survey and presents the simulation method. Section 3 uses the results of the simulations to show how the quality of income data affects the measurement of inequalities in daily travel and transport expenditure for individuals and households. Section 4 concludes on the benefits of detailed individualised income data collection for the measurement of inequalities in daily mobility and in transport expenditure.

DATA AND METHOD

The PMU survey ("Pauvreté et Mobilité Urbaine", Poverty and Urban Mobility) carried out in 2003 aimed to analyse the links between poverty, daily mobility and access to urban services in Douala1 . Urban areas were stratified according to the availability of urban services, how long ago they became urbanised, distance from the centre and major roads, and the standard of living of the residents. Thirty survey zones were then selected within the stratified areas and the sample of households was selected randomly within the survey zones. 600 households and 1885 individuals of over 10 years of age were surveyed by face-to-face interviews in their home [START_REF] Sitrass | Poverty and Urban Mobility in Douala[END_REF].

The study zone

Douala is Cameroon's most populous city, with nearly 2 million inhabitants in 2003. It is also a port and the main gateway for imports and exports. Douala is the country's economic capital and provides the location for more than half the country's economic activity and industrial production. Economic activity is nevertheless dominated by the informal sector which employed 62% of the workforce in 2005. As a result of the low level of wages, 14% of the population have at least two professional activities (De Vreyer and Roubaud, 2013).

The city has developed in a site that is subject to severe geographical constraints. Some informal districts have sprung up in swampy zones or on natural drainage courses or slopes. The Wouri River which crosses the city also poses a major constraint for transport, since the only bridge between the two banks creates a notorious bottleneck (Figure 1). * The nearest public transport stop is less than 15 minutes away on foot ** The nearest public transport stop is 15 minutes or more away on foot As in other cities of sub-Saharan Africa, in Douala walking is still the population's principal means of transport. Access to private vehicles is very limited and motorised trips are mainly made on public transport [START_REF] Diaz Olvera | The puzzle of mobility and access to the city in Sub-Saharan Africa[END_REF] which is provided by six modes: shared taxi, motorbike taxi, minibus, bus, light truck, undeclared cab. Most public transport trips are made by shared taxis, but the modal share of motorbike taxis is rapidly increasing, as they are less expensive over short distances and can provide a door-to-door service. The ease with which residents can access a public transport mode from their home varies according to the availability of roads and public transport in the district in which they live and access and egress segments made on foot may be long. Walking access and egress times allow us to identify which of the survey zones are accessible -when the place of residence is on average less than 15 minutes from the loading point -, and which zones are remote -when it is 15 minutes or more away 2 .

2 This dichotomous spatial indicator is crude, due to a lack of exhaustive data about the districts' accessibility and facilities. It does not allow us to measure a gradient of increasing difficulty in access and only takes account of one dimension of the accessibility problem, namely access to public transport.

Capturing professional activities and income in the PMU Survey

The PMU survey collected data at two levels. First, at the level of the household, the reference individual provided information on the composition of the household, the dwelling, and access to basic services and infrastructure. Second, each individual of over 10 years of age was interviewed personally, with the focus placed on his or her socio-economic characteristics, access to private vehicles, expenditure on transport and trips made on the day before the interview.

With regard to socio-economic characteristics, several sets of questions provided precise information about each individual's professional activities and income 3 . First of all, a set of questions allowed us to list each professional activity exercised by the respondent. Each individual was asked if he/she was currently engaged in a professional activity and if so:

1. the nature of the principal activity, its frequency (over the last 12 months and the last 30 days) and for how long the individual had been doing it (Figure 2). This information allowed us to calculate annual incomes; 2. the description of any remunerated secondary activities (Figure 3). A secondary activity is defined as a supplementary professional activity practiced by an individual currently in employment (i.e. in the past 30 days)4 .

No. Question 29. Have you been gainfully employed (in cash or in kind) in the past 30 days? 30. Is this a permanent job? 31. Are you a salaried employee? 33. Description of principal activity 39. For how long have you been engaged in this activity? (number of years) 40. How many months did you work out of the past 12 months? 41. How many days did you work out of the past 30 days?

Fig. 2. Identification of principal activity in the PMU survey

3 By interviewing each respondent it is possible to overcome biases which result from the use of a single informant for an entire household [START_REF] Fisher | Who should be interviewed in surveys of household income?[END_REF]. Insofar as the reference individual is not necessarily correctly informed about the situation of each household member, it would appear to be questionable to rely only on his or her statements.

No. Question 36. Do you have other activities that generate income in cash or in kind? 37. How many? 38. What are these activities?

Fig. 3. Identification of secondary professional activities in the PMU survey

With regard to income, our aim was to assess as accurately as possible the individual's total monetary resources, by mentioning a variety of potential sources, which may or may not be linked to professional activities (Figure 4). Respondents were left free to estimate their earnings from each source according to the most appropriate periodicity. There are two advantages to this more detailed data collection procedure:

-As an individual can have several sources of income, listing them during the interview helps to reduce omissions;

-Whatever the periodicity reported by the respondent, each type of income can be extrapolated on a monthly or annual basis in order to estimate a total sum.

In this paper, we have harmonised the separate incomes to express them in monthly terms, then consolidated them for each individual; the sum of individual incomes has been used to estimate the household's total income.

The survey protocol makes it very clear that the income data should relate to money earned outside the household in order to avoid double counting. In particular this prevents the counting of monetary transfers between members of the household (pocket money, paying for meals taken outside the household). Particular attention was paid to the collection of income data during the training of field staff in order to make them aware about variable periodicities, the difference between turnover and profit and the need to avoid double counting if several members of the household take part in the same economic activity.

No.

The evaluation of income data in the PMU survey

It is possible to compare the sources of income that were collected in the PMU survey with those collected during a survey that dates from 2002, namely the CAVIE survey (INS, 2003). This survey collected information on the living conditions of 7500 households: infrastructure and basic services, services in the dwelling, durable goods. Household composition and information on all members of the household were also included in the survey.

Two major methodological differences with the PMU should be noted:

a single informant was questioned in each household in order to provide not only general information about the household, but also specific information on each individual; the single informant was asked whether each member of the household had worked in the last twelve months (and if so in which sector), about his/her main sources of income and the sums involved, broken down into two categories, professional and other. These two amounts were expressed as a bracket.

As a result of these methodological differences, the distribution of individuals (of over 10 years of age) according to the principle source of income differs considerably between the two surveys (see the second and third columns of Table 1). While the CAVIE survey reports that one in two individuals had no income, the PMU survey gave a ratio of one in four. The differences were moderate when we compared the proportions of individuals whose work was their principal source of income, but the PMU survey reported a higher proportion of individuals receiving pensions or rents and, in particular, receiving mainly gifts. This is because the information relating to the individual was collected directly from him/her and also because these sources of income were identified specifically in the questionnaire (Questions 55 to 58, Figure 4). The sums involved were often small, particularly in the case of gifts5 . Nevertheless, these gifts from outside the household were frequently the only source of income for schoolchildren and the economically inactive.

Measuring mobility inequalities, simulating degraded data collection

Mobility practices were measured using two categories of indicators:

-Physical indicators, which were measured at the individual level, are the number of trips (total and motorised) and the travel time budget (total and motorised).

-Monetary indicators were estimated for individuals and for households. In both cases, the monthly expenditures on urban transport, for all modes and solely for public transport modes, were computed6 . The proportion of household income spent on urban transport was also calculated.

Inequalities have been evaluated using concentration curves and concentration indices group's share of the indicator will be exactly equal to its relative size in the population. In this case, the cumulative percentages of both the indicator and the population will be exactly equal whatever population segment is considered. Graphically, the closer the plot is to the line of equal distribution (the first diagonal), the more equally the indicator is distributed among the population and the lower its concentration index. Mathematically, the latter is equal to 1 minus twice the surface area between the plot and the abscissa.

In order to produce a concentration curve or index it is therefore necessary to be able to class the population of individuals or households according to their standard of living. In the case of individual mobility indicators, the individual's income provides a better idea of his/her ability to access motorised modes than the income of the household [START_REF] Diaz Olvera | Household transport expenditure in Sub-Saharan African cities: Measurement and analysis[END_REF] and therefore allows us to estimate the individual's standard of living. In the case of household indicators, ranking households according to their total income means that a given income provides the same standard of living to an individual living alone, a couple, or a family with several children. In order to make the conversion from income to standard of living, economists use an equivalence scale that expresses the differing needs of different individuals (adults and children in particular) and the economies of scale that result from household size (e.g. a couple

does not necessarily need twice the amount of space in their home as a single person).

Determining an equivalence scale is however a complex problem that has raised much controversy [START_REF] Lechêne | Une revue de la littérature sur les échelles d'équivalence[END_REF]. In the absence of a consensus, we adopt what Deaton and Zaidi have termed the "arbitrary method" (2002:51) which involves, in the case of poor countries, considering a low cost for a child and a low economy of scale coefficient, in our case respectively 0.25 and 0.10. The number of individuals in the household is thus replaced by a number of consumption units which is equal to:

(A + α . K) (1-β) where A is the number of adults, K the number of children, α = 0.25 and β = 0.10. The standard of living of the household is then estimated on the basis of the total household income divided by the number of consumption units. Finally households are ranked according to these estimated standards of living.

This methodological basis allows us to calculate mobility inequality indicators, when an estimate of individual incomes is available. An additional stage is necessary in order to assess how the precision of income data collection affects the measured mobility inequalities. This consists of comparing the observed value of the indicator with that which would have been obtained if the distribution of individuals according to their principal source of income had been the same in the PMU and CAVIE surveys. We are, of course, unable to observe this situation.

However, we can use the available data to simulate it.

The simulation method can be summarised as follows. The distribution of individuals on the basis of their principal source of income as reported in the CAVIE survey, which identified more individuals without incomes, was applied to the sample from the PMU survey, which meant that randomly selected respondents had their incomes reset to zero. The proportion of such individuals with their incomes reset to zero depends on the nature of their principal source of income (see last column in Table 1). It was 11.4% when the principal source of income was labour, i.e. approximately one in nine individuals in this category, 55.9% when it consisted of allowances, rents or other sources and 86.9% when gifts were the principal source of income.

In each simulation the distribution of individuals according to their principal source of income was therefore equivalent to that obtained from the CAVIE survey 7 .

To correct for the random nature of resetting the income of one individual to zero rather than another, we carried out a large number of simulations in order to estimate the stability of the 7 This simulation strategy allows us to simulate "realistic" populations. In the simulations, each individual's mobility is accurately estimated, but the individuals (and therefore the households) are incorrectly classified because the data on their income is incorrect. The error in the estimation of inequality is therefore due to the combination of two sources of error: an erroneous classification of individuals and an erroneous estimation of mobility for a given income level. This simulation method was preferred to one which involves directly duplicating the individuals that are already present in each principal income source category until a distribution similar to that in the CAVIE survey is obtained. This is because an alternative strategy of this type would accurately estimate mobility for each income level thereby eliminating a potential source of error in the inequality calculation.

mobility inequality measures. For each inequality measurement, the value observed in the PMU survey can be compared to the median of the simulated values, as well as to the amplitude of the distribution of the simulated values8 . We thus determined, for each inequality measurement, the number of simulations that is required in order for the estimates of the median value and the amplitude to become stable. This number varied slightly depending on the inequality measurement in question, but never exceeded 500. The results presented below are therefore based on a unique set of 500 simulations.

IMPACTS OF THE INCOME DATA COLLECTION METHOD ON THE MEASUREMENT OF MOBILITY INEQUALITIES

We shall begin by considering the physical indicators of mobility, then move on to the monetary indicators. For a given mobility indicator, if the observed value of the inequality measurement and the median simulated value are close together and the dispersion of the simulated values is small, the income data collection method has little impact on the mobility indicator. If there is a large disparity between the two values, particularly if the observed value is outside the range of the simulated values, it means that our perception of the inequalities is biased when the income data is collected in a simplified manner.

Inequalities according to physical indicators

The total number of trips and the daily travel time budget are the indicators that are the most equally distributed according to the income of individuals. As shown by Figure 5, they are also those for which the impact of a precise measure of income is the most limited: the median of the simulated values is indistinguishable from the observed value and the range of the simulated values is very narrow. Differences for these mobility indicators according to income tend to diminish because citizens with low income or no income at all compensate for their lower access to motorised modes by intensive walking. This explains why the values of the corresponding concentration indices are close to zero9 .

Fig. 5. Observed and simulated concentration indices for number of trips and travel time budget (all modes and motorised modes)

The benefits of collecting accurate income data increase when the travel indicators are limited to motorised modes. As can be seen in Figures 6 and7, the plots for the simulated income distributions are above the plot for the observed distribution 10 and the largest differences between curves are concentrated in the bottom half of the distribution. This means that collecting aggregated data reduces inequalities with regard to motorised travel. With regard to the concentration indices (not shown here), the observed value is at best indistinguishable from the upper bound of the range of simulated values and at worst above this bound. The simulated concentration indices are about 90% of those obtained for the observed data. It is important to note that this underestimate does not affect the entire population in the same way and is essentially due to an inaccurate evaluation of the situation regarding the poorest half the population, as shown by the concentration curves.

10 In order to improve the comprehensibility of the figures and facilitate their interpretation, only six curves have been plotted for each: that obtained directly from the PMU survey and five simulations randomly chosen from amongst the five hundred. If we take account of the residential location of the individual's household, distortions in our representation of spatial inequalities become apparent. Once again, the effects are rather negligible in the case of the indicators for all modes (Figure 8). However, use of motorised modes, which is more unequally distributed within remote zones, is more inaccurately measured when income data collection is simplified. For these districts, the observed inequality is greater than the simulated values while it is near the median of the simulated values for the accessible zones. Moreover, the range of simulated values is very large in the case of the remote zones and leads to a partial superimposition of the distributions of simulated values for the two types of zones. Consequently, in between 1% (number of motorised trips) and 2% (motorised travel time budget) of simulations, inequality is greater in the accessible zones than in the remote zones, while the observed concentration index is greater in the remote zones than in the accessible zones by almost half. Excessively aggregated collection of income data may therefore lead to an underestimation of inequalities in each type of zone, and sometimes to a false impression of the relative situation in the two types of zone.

Inequalities according to monetary indicators

The benefit of the precise estimation of incomes is even clearer when we consider the concentration of individuals' travel expenditure (Figures 9 and 10). Once again, almost all the simulated plots are above the observed plot throughout the distribution. The differences are particularly marked for the bottom half of the distribution. The result is a significant underestimate of the inequalities as the concentration indices for the simulated values only attain 85% of those for the source data.

Remote area R

Households spend on average 17% of their budget on daily travel, but this proportion varies according to their standard of living. As can be seen in Figure 13, transport accounts for a lower share of expenditure as households become more well-to-do. According to the observed values, daily travel absorbs almost a quarter of the resources of the poorest households (first quartile), a fifth of those in the second quartile and about a seventh of those in the most well-to-do half of the population (quartiles 3 and 4). The simulated distributions also show a tendency for the budgetary coefficient to fall as household resources increase. But the estimated coefficients are in this case systematically greater than those that have been observed, the bias once again varying greatly according to the wealth of the household. The situation of the more well-to-do is accurately represented, but there is an overestimation of 4% for the two intermediate quintiles and of approximately 50% of the total income in the case of the poorest households. In the case of this last group, the coefficients obtained from the simulations are clearly totally unrealistic.

Such high values would mean that households would then have only a very small proportion of their income left to live on (food, housing, education, clothes, etc.).

Q1 corresponds to the poorest households and Q4 to the wealthiest. By taking account of residential location we can observe similar trends: there is a deterioration in the quality of the estimation from the wealthy to the poor which leads to unrealistic estimations for the first quartile whatever the type of zone (Figure 14). There is also a relative inversion of the position of the two types of area for the poorest half of the population. Once again, incomplete or inaccurate income data collection leads to an erroneous estimate of the budgetary coefficient of transport, in particular for the poorest households.

Q1 corresponds to the poorest households and Q4 to the wealthiest.

Fig. 14. Proportion of household income devoted to daily mobility, according to income quartile and type of residential zone

CONCLUSION

The income data collection method used in the PMU survey removes the majority of the difficulties that were mentioned in the introduction:

the detailed listing of professional activities of whatever nature and scale makes it easier subsequently to collect more reliable data on income from work;

the explicit mentioning of a variety of sources of income (gifts, pensions, rents, etc.) considerably increases the reported sums; allowing the respondent to select the periodicity with which he or she reports income brings the situation described in the survey closer to real practices; conducting a specific interview for each individual avoids the need to rely on a single informant who may not be very well aware of the situations of individual household members.

However, the methodology that we have chosen does not allow us to perceive the scale of the pooling of individual income within the household, but the opening of the "black box" of the household (Alderman et al., 1995:15) remains a theoretical and empirical problem.

Of course, these options are expensive in terms of both respondent burden and survey cost. But our analyses have shown that more precise data collection improves the estimation of mobility inequalities. Indeed, the data collection method has a direct impact on the ranking of individuals and households in terms of standard of living. In turn, the ranking of individuals and households has impacts on the measurement of inequalities as regards mobility and transport expenditure.

Our analysis shows that the effect of more accurate income data is minor in the case of aggregated indicators (e.g. overall number of trips, travel time budget for all modes, or household level indicators) and for the most affluent groups (individuals and households). On the contrary, the most significant impacts concern disaggregated indicators (e.g. number of motorised trips, motorised travel time budget or individual level indicators). But when there is an effect, it is systematically in the same direction. Simplified data collection tends to minimise the scale of inequalities and the error is greater in remote zones than in accessible zones. This differentiated effect is absolutely clear, in spite of the limitations of our spatial indicator. It is also to some degree independent of the effect of the household's standard of living. Finally, the errors in the ranking of households lead to estimate, in the case of the poorest households, very high and therefore improbable proportions of household income spent on transport. Shortcomings in the methodological apparatus blur our perception of the social and spatial situation of underprivileged groups and distort our assessment of mobility inequalities.

Ultimately, they impede investigation of the links between daily travel, poverty and social exclusion. It seems essential to improve the way income data is collected in surveys in order to obtain a more accurate picture of the mobility inequalities linked to households' and individuals' standards of living and their residential location. This need applies beyond the case of Douala. Making similar comparisons to those presented here in other urban contexts, in other African countries, or even in other developing or developed regions, would allow us to evaluate the extent to which the lessons we have learned from Douala can be generalised. Nevertheless, similar effects to those we have revealed in Douala are likely to pertain to other African cities. The reason for this is that large African cities share a considerable number of features: the jobs market is dominated by the informal economy, there are large inequalities with regard to income and widespread poverty, rapid spatial expansion, a lack of basic facilities, low private vehicle ownership rates and a public transport system which is informal, inefficient and unsubsidised. In situations of this type it is particularly important to be able to evaluate accurately the redistributive nature of urban public transport policies. A thorough knowledge of daily travel practices is one requirement for this and accurate collection of individual income data is another which is just as essential.

Fig. 1 .

 1 Fig. 1. The conurbation of Douala and the survey zones in the PMU household travel survey(2003)

  Fig. 4. The collection of individual income data in the PMU survey

(

  [START_REF] O'donnell | Analyzing Health Equity Using Household Survey Data: A Guide to Techniques and their Implementation[END_REF]. The concentration curve provides a graphic representation of the proportionality of the distribution of an indicator (number of daily trips, travel time budget, transport expenditure) in relation to the population (individuals or households), which is ranked according to increasing income. It plots the cumulative percentage of a mobility indicator (yaxis) against the cumulative percentage of the population, ranked from the poorest to the richest (x-axis). If the indicator is distributed among the population in a perfectly equal manner, any

Fig. 6 .

 6 Fig. 6. Concentration curves for number of motorised trips: observed distribution and five simulated distributions of individual income

Fig. 8 .

 8 Fig. 8. Observed and simulated concentration indices for number of trips and travel time budget (all modes and motorised modes), according to type of residential zone

Fig. 9 .

 9 Fig. 9. Concentration curves for public transport expenditure: observed distribution and five simulated distributions of individual income

Fig. 11 .

 11 Fig. 11. Observed and simulated concentration indices for individual and household transport expenditure

Fig. 13 .

 13 Fig. 13. Proportion of household income devoted to daily mobility, according to income quartile

  Type of monetary resources (CFA francs)

		Do you	Periodicity	Amount
		receive...	1. Daily
		1. Yes	2. Weekly
		2. No	3. Monthly
			4. Quarterly
			5. Half-yearly
			6. Annually
			7. Other ..........
	51.	Wages / salary / profit from principal activity
	52.	Wages / salary / profit from secondary activity (activities)
	53.	Wages / salary / profit from other professional activities
	54. Total labour income (51+52+53)
	55. Annuities
	56.	Grants, gifts, alimony, allowances, etc. (from persons outside household)
	57. Family allowances, pensions, scholarships
	58.

Table 1

 1 Distribution of individuals according to their principal source of income and probabilities used to simulate income distributions for the PMU survey sample

		PMU survey	CAVIE survey	Relative
		(%)	(%)	disparity
		(a)	(b)	(a-b)/a
	Individuals with an income	74.5	48.5
	Professional activities	49.4	43.8	0.114
	Allowances, rent or other	4.5	2.0	0.559
	Gifts	20.6	2.7	0.869
	Individuals with no income	25.5	51.5
	Total	100.0	100.0

The PMU survey was carried out by a team composed of French and Cameroonian researchers, including the authors of this paper, who were responsible for the project's general methodology, in particular the survey questionnaire.

The level of multiple activities measured by the PMU survey was 12%, which is close to the value obtained by De Vreyer and Roubaud (2013).

These gifts accounted for less than 10% of all the income reported in PMU survey. They accounted, of course, for an even smaller proportion according to the CAVIE survey, but it is impossible to calculate the exact percentage as income data was only recorded in the form of a bracket.

To collect information on public transport expenditure, individuals were asked how many times they used each of the six modes of public transport and the corresponding amount spent during the past seven days. In motorised households, the running costs of vehicles were collected on a monthly basis (fuel) or annually (maintenance, repairs, insurance, licensing).

The central tendency parameter of the distribution of the inequality indicators calculated from the simulated incomes is the median rather than the mean value, due to the risk of extreme values appearing in the case of some simulations. For the same reason, when the amplitude of the distribution of the inequality indicators was estimated, the 2.5% of extreme values at the bottom and the top of the distribution were excluded.

As the concentration plots for the number of trips and the travel time budget for all modes are almost flat and indistinguishable from the first diagonal, they are not shown here.