Céline Boiteux-Orain

Rachel Guillain

Économiques Umr5118

LABORATOIRE D'ANALYSE ET DE TECHNIQUES

Keywords: producer services, information technologies, monocentric and polycentric configurations, suburbanization. JEL Classification: R I2, R30

Changes in the intra-metropolitan location of producer services in Ile-de-France (1978-1997) : do information technologies promote a more dispersed spatial pattern ?

INTRODUCTION

Advances in information technologies were expected to herald the impending demise o f the urban core as the prime focus for information interaction [START_REF] Webber | The urban place and the nonplace urban realm[END_REF][START_REF] Kellerman | Telecommunications and the geography o f metropolitan areas[END_REF][START_REF] Down | Living with advanced telecommunications[END_REF]. The main arguments for this were that (i) with information technologies, an impressive mass of information can be reliably transmitted anywhere in real time [START_REF] Graham | Cities in the real-time age: The paradigm o f telecommunications to the conception and planning of urban space[END_REF]; (ii) continued progress in information technologies would greatly reduce communication costs; and (iii) information technologies would replace face-to-face contacts [START_REF] Gaspar | Information technology and the future of cities[END_REF].

'For the first time in histoiy, it might be possible to locate on a mountain top and to maintain intimate, real-time, and realistic contact with business or other associates. All persons tapped into the global communication net would have ties approximating those used today in a given metropolitan region* [START_REF] Webber | The post-city Age[END_REF], quoted in Moss, 1987, p. 535).

All else being equal, it was expected that economic activity would be more evenly distributed. Yet economic activity and more particularly information-dependent activities such as services and business administration continue to concentrate in cities [START_REF] Sassen | The Global City[END_REF][START_REF] Daniels | Service Industries and the World Economy[END_REF]. It seems, then, that the connections between the location of information-dependent activities and information technologies are more complex than was first thought. Face-to-face contacts still appear to be an agglomeration force for information-dependent activities. In other words, information technologies and faceto-face contacts cannot be considered as substitutes. This idea has received a great deal o f empirical support in North America [START_REF] Coffey | Forward and backward linkages of producer-services establishments: evidence from the Montreal metropolitan area[END_REF][START_REF] Coffey | The intrametropolitan location of high order services: Patterns, factors and mobility in Montreal[END_REF][START_REF] Longcore | Information technology and downtown restructuring: The case of New York City's financial district[END_REF][START_REF] Leslie | Abandoning Madison Avenue: Relocalisation o f advertising services in New York City[END_REF], yet few such studies have been conducted in France.

In this paper, we seek to further our understanding o f the role played by new information technologies in the present-day distribution o f information-dependent activities in Ile-de-France. More precisely, we use data on employment by place of work to investigate the changing spatial distribution o f producer services sector employment in this metropolitan region between 1978 and 1997. We then seek to answer the questions: (1) do FIRE (Finance, Insurance and Real Estate) and business services decentralize, moving away from the CBD during the study period in greater numbers than activities that are less information-dependent? If so, (2) are they scattered across the entire metropolitan region or do they cluster rather in new employment poles in the suburbs alongside other activities? And finally, (3) do all the separate sectors o f producer services display the same propensity to suburbanize?

To answer these questions, two complementary approaches are adopted. The spread of information-dependent activities (both overall and by separate sectors) over the period 1978-1997 is examined in terms of rings. However, this approach is not sufficient in itself. If the decentralization of employment in producer services takes the form of scatteration1, then there has been a decline in the role o f face-to-face contacts. Conversely, if high-order activities leave the CBD to form new employment poles in the peripheiy, the role of face-to-face contacts apparently remains an important location factor for such activities. Therefore, we also conduct an analysis in terms o f employment poles to investigate these subsidiary questions.

Our results show that producer services are indeed suburbanizing in Ile-de-France. However, suburbanization is not synonymous with scatteration. It exhibits a subtle multicentric pattern with specialized centers forming outside the CBD. These results suggest that face-to-face contacts may still be instrumental in explaining the urban pattern.

The next section reviews the literature about the'im pacts of new information technologies on the geography of economic activity. Then we describe the study area, data and methodology used in conducting our empirical study. The following two sections examine the changing spatial distribution o f high-order service employment in Ile-de-France over the period 1978-1997. Then, we examine to what extent information facilities may reinforce this spatial distribution by highlighting the impact of fixed costs. In our final section, we summarize the main characteristics o f suburbanization in Ile-de-France and discuss the effects of information exchanges on this process.

THE SPATIAL IMPACTS OF INFORMATION TECHNOLOGIES:

A CONTROVERSIAL ISSUE

It is difficult to apprehend the effects o f information technologies on the location of economic activities. Indeed, these technologies are still recent developments and their overall impact on the location choice of activities may take some time to work through. Some authors claim that information technologies will bring about radical changes in spatial organization, much as the railroads or the automobile did in their time [START_REF] Hohenberg | The Making o f Urban Europe, 1000-1950[END_REF]Rallet, 1999a). This is a realistic claim. First, information can be transmitted easily via information technologies between distant agents, thereby freeing economic agents from their proximity constraints. Second, economic activity is becoming increasingly information-based [START_REF] Sassen | The Global City[END_REF][START_REF] Castells | The rise o f the Network Society[END_REF].

The greatest spatial impact of information technologies will be on services and business activities, because these activities are information intensive. Indeed, they are based on complex decision-making processes, which renders them highly informationdependent. These activities are traditionally located in city centers because of their information requirements. Information exchanges have a strong non-market dimension and the benefits derived from information exchanges are similar to those derived from externalities [START_REF] Jaffe | Real effects o f academic research[END_REF][START_REF] Feldman | The Geography o f Innovation[END_REF][START_REF] Audretsch | R&D spillovers and the geography of innovation and production[END_REF][START_REF] Fujita | The formation o f economic agglomerations: Old problems and new perspectives[END_REF][START_REF] Guillain | The local dimension o f information spillovers: A critical review of empirical evidence in the case of innovation[END_REF]. Moreover, distance is a barrier to the spread o f information [START_REF] Hägerstrand | Aspects o f the spatial structure of social communication and the diffusion o f information[END_REF][START_REF] Baneijee | The economics of rumours[END_REF], and accordingly information exchanges generate spatial externalities. Because the information diffusion is spatially restricted, information-dependent activities are located close to each other. Ogawa andFujita's models (1980,1982) explain the trade-off between the benefits derived from information externalities and the high costs of central location incurred by firms. They develop a model of firm-household interactions with information externalities. This model aims at determining the equilibrium configurations o f a city where information exchanges between firms act as an agglomerative force. Opportunities for information exchange increase with the number of firms sharing the same location. Furthermore, the firms are assumed to have different information. Consequently, by facilitating a larger number o f diversified contacts, geographic proximity ensures that agents can acquire a large quantity o f varied information. Proximity between firms thus cuts their operating costs and boosts profits. Households simply have to move toward these firms to find work. However, the clustering of many firms within a single area pushes up land rent and commuting costs: these are the dispersion forces, which are disincentives to any further agglomeration by firms. At equilibrium, the distribution of firms and households exhibits patterns with one or more centers formed by the agglomeration o f firms. These patterns result from the balancing out of the two opposing forces. [START_REF] Sekeris | Externalities and the formation o f cities[END_REF] introduces two types of firm into this model: manufacturing activities and services. Services are assumed to be more sensitive to information externalities than manufacturing is. At equilibrium, services are more concentrated in the centers). Thus, the more sensitive activities are to information externalities, the closer together they will locate.

By introducing information technologies into this reasoning, it can be argued that information-dependent activities will leave the high-rent city centers. Information technologies seem to weaken the proximity constraint on information exchanges. They also seem to provide the same advantage as city centers for efficient information exchanges without the economic, social and environmental diseconomies of urban concentration.

However, the recent literature on the spatial impact o f information technologies is not so sure about this prediction. Indeed, the evidence is that some activities, especially producer services, still cluster in the city centers because their informational component acts as an agglomerative force despite advances in information technologies [START_REF] Daniels | Service Industries and the World Economy[END_REF][START_REF] Bailly | Localisation des services à la production et restructurations économiques [Producer services localization and economic restructuring[END_REF][START_REF] Coffey | La décentralisation des services supérieurs dans la région métropolitaine de Montréal, 1981-1989 [The decentralization o f high order services in the Montreal metropolitan region, 1981-1989[END_REF][START_REF] Sassen | The Global City[END_REF]. In order to explain the links between information exchanges and localization and thus the spatial impact of information technologies, the specific character o f the information has to be analyzed.

In short, two main types of information can be identified [START_REF] Guillain | The local dimension o f information spillovers: A critical review of empirical evidence in the case of innovation[END_REF]. 'Codified information', being systematic, repetitive and articulated can be transmitted easily and reliably by information technologies. Tacit inform ation, by contrast, requires dialogue between parties and gradual clarification because it is highly personalized and contextualized (Foray and Lundwall, 1996).

The persistence o f tacit information in the economy is one explanation for the continuing need for proximity in information exchanges. New advances in information technologies simply increase the opportunities for transmitting codified information over long distances but do not change the proximity constraint related to tacit information (RaUet, 1999b;[START_REF] Guillain | The local dimension o f information spillovers: A critical review of empirical evidence in the case of innovation[END_REF]. Indeed, geographic proximity facilitates and enhances the understanding of tacit information for a number of reasons. First, there are more opportunities for exchanging information where there is a highdensity o f individuals. Next, proximity means that time spent arranging contacts can be saved, and therefore more interactions are possible. Finally, geographical proximity is conducive to multiple contacts and so induces other forms o f proximity, more particularly relational proximity [START_REF] Bouabdallah | Politiques technologiques et structuration institutionnelle d'un système d'innovation : stratégies d'acteurs et appropriation des règles [Technological policies and institutional structuring of an innovative system: Actor strategies and rule appropriation[END_REF]. With frequent encounters, individuals share the same culture, a common language and similar outlooks. Moreover, mutual confidence develops between agents, precluding opportunistic behavior [START_REF] Arrow | The limits o f Organization[END_REF][START_REF] Granovetter | Economic action and social structure: The problem o f embeddedness[END_REF][START_REF] Cohen | Absorptive capacity: A new perspective on learning and innovation[END_REF][START_REF] Pryke | An international city going "global": Spatial change in the city of London[END_REF]Saxeman, 1994;[START_REF] Thrift | New urban eras and old technological fears: Reconfiguring the goodwill of electronic things[END_REF]. Proximity therefore allows improved transmission of information, more refined interpretation and consequently better use of that information [START_REF] Guillain | Villes et échanges d'informations[END_REF][START_REF] Guillain | The local dimension o f information spillovers: A critical review of empirical evidence in the case of innovation[END_REF].

We set out to test the robustness of the second thesis about the impacts o f information technologies in Ile-de-France through an empirical analysis of the distribution of employment.

STUDY AREA, DATA AND METHODOLOGY

With nearly 11 million inhabitants and approximately 5 million jobs, He-de-France is France's largest region. It represents 18.8% of the national population and produces 29% o f the national GDP, so that GDP per inhabitant in this region exceeds the national average by 55%. The economy of Ile-de-France is largely oriented toward the service sector: 80% o f regional employment is in this sector, compared with 72% nationwide (IAURIF, 2001). The region covers 12,000 square kilometers, which is 2.2% of the national land area. It comprises 1280 communes and the 20 districts of the City of Paris. Since 1964 the metropolitan region has been partitioned into eight departments: Paris, Seine-et-Mame, Yvelines, Essonne, Hauts-de-Seine, Seine-Saint-Denis, Val-de-Marne and Val-d'Oise.

We used two separate databases to conduct our empirical analysis. Our first source of data was the Population Censuses compiled by the French National Institute o f Statistics and Economic Studies (INSEE) for the years 1975, 1982, 1990 and 1999. These data relate to the communal level. The second source o f data was the 1978 and 1997 surveys conducted by INSEE, providing information on public-and private-sector employment by place o f work. These employment data are classified according to the INSEE's industrial classification, NAP 600 ('Nomenclature des Activités Professionnelles') for 1978 and NAF 700 ('Nomenclature d'Activités Française') for 1997. These sectorbased definitions were standardized to ensure that the two years o f the study period could be reliably compared.

To examine the data in accordance with the objectives set out in the introduction, we adopted two approaches. The first was to analyze changes in the spatial distribution o f employment during the 1978-1997 period by 'rings'. The Ile-de-France region was divided into three rings (see fig. 1) on the basis of the standard division: Paris, Petite Couronne2 (our inner ring) and Grande Couronne3 (our outer ring).

[Fig. 1 about here]

The second approach was a method o f identifying employment poles. The choice of such a method is somewhat problematic. Indeed, empirical literature on this subject suggests a whole battery o f criteria for defining employment poles, the most common being total employment levels, employment density cut-offs, employment-to-population or employment-to-resident worker ratios, or any combination thereof [START_REF] Mcdonald | The identification of urban subcenters[END_REF][START_REF] Giuliano | Subcenters in the Los Angeles region[END_REF][START_REF] Mcdonald | Suburban employment centers: The case of Chicago[END_REF][START_REF] Cervero | Polycentrism, commuting and residential location in the San Francisco bay area[END_REF][START_REF] Forstall | Defining job concentrations: the Los Angeles case[END_REF][START_REF] Cervero | Sub-centering and commuting: Evidence from the San Francisco bay area, 1980-1990[END_REF][START_REF] Mcmillen | Suburban subcenters and employment density in metropolitan Chicago[END_REF][START_REF] Bogart | Employment centers in greater Cleveland: evidence of evolution in a formerly monocentric city[END_REF]Shearmur and Coffey, 2000;[START_REF] Anderson | The structure of sprawl: Identifying and characterizing employment centers in polycentric metropolitan areas[END_REF].

However, these criteria have mainly been tested on large North-American urban regions. When trying to apply them directly to the Ile-de-France, two main problems arise. First, unlike North-American cities, but like most European cities, the central part o f the Ile-de-France area is characterized by a high concentration o f both population and employment, so that standard employment-population indexes are not very useful. In particular, the use o f such indexes in the Ile-de-France region entails excluding some sizeable employment areas, both in the central part o f the metropolitan region and in the suburbs. Therefore, in order to identify areas with comparatively more jobs than inhabitants, we propose a new criterion, which we term an employment location quotient. This employment location quotient is defined as the ratio o f the employmentpopulation ratio of a given commune to the employment-population ratio o f the department in which this commune is located. Thus, an employment location quotient of more than one indicates that the given commune has ah employment-population ratio that exceeds that of the entire department, or, in other words, that this commune has a higher proportion o f employment to population than do the communes o f the department as a whole.

Second, a specific feature o f this region is the presence o f a 'megapole' o f almost two million jobs, constituted by the City o f Paris and its western and northern extensions into adjacent areas o f the inner ring. To the best of our knowledge, two solutions have been proposed in the literature to tackle this problem. The first solution, used for example by [START_REF] Mcmillen | Suburban subcenters and employment density in metropolitan Chicago[END_REF] for the Chicago metropolitan area, consists in raising the minimum employment cut-off level for the giant center in order to divide it into a number o f employment subcenters. An alternative solution, adopted by [START_REF] Bekouche | La recomposition du centre économique parisien [The restructuring of the economic center in Ile-de-France[END_REF] for Ile-de-France, is to group the various spatial units of the large pole according to their economic profile. Insofar as any reasonable subdivision of the megapole requires the use o f several cut-offs for minimum employment levels, we have opted for the second approach.

To account for these two specific features of the Ile-de-France region, we adopted a three-step procedure to determine employment concentrations.

First, we defined a suburban employment pole as a suburban commune, or a set o f adjacent suburban communes, concentrating at least 7,000 jobs and with an employment location quotient o f more than unity.

Second, using the methodology described above, the 20 districts o f the City o f Paris and the 15 inner communes o f the megapole were grouped into employment poles according to their 1997 economic profile (Fig. 2 and Fig. 3).

[Fig. 2 and Fig. 3 about here]

Third, adapting an approach used by Shearmur and Coffey (2000), all the poles identified in the preceding steps were grouped into three main categories: central poles (poles containing at least one commune of 50,000 jobs); primary poles (poles in which one or more communes have a minimum of 15,000 jobs) and isolated poles (poles formed by a single commune containing at least 7,000 jobs). This three-step procedure was applied to the 1997 data and replicated for the 1978 data. It led to the identification of 34 employment poles (Table 1 and Fig. 4).

[Table 1 and Fig. 4 about here]

CHANGES IN THE GENERAL SPATIAL PATTERN IN ILE-DE-FRANCE, 1978-1997

In this section, our aim is to determine, by two means, whether new information technologies have made face-to-face contacts obsolete as the main factor in the location of high-order activities. We begin by analyzing whether employment in this sector has become more or less evenly distributed across the three rings defined in the previous section compared with less information-dependent activities. Next, we examine the sectoral composition of employment poles to determine whether producer services tend to disperse across the remainder o f the region or to concentrate in suburban employment poles.

In order to conduct this part of our empirical analysis, we aggregated employment data into the nine following broad sectors; (1) Industry; ( 2 Table 2 summarizes changes in employment distribution across the rings for the nine sectoral groups under consideration.

[Table 2 about here]

Analysis based on the rings reveals that the 1978-1997 period was one of decentralization o f employment from the heart of the region toward the suburban areas, and especially the outer ring. While Paris's share o f total metropolitan employment fell from 41% to 32% between 1978 and 1997, the share o f total metropolitan employment in the outer ring rose from 23% to 31%. This suburbanization o f total employment led to a more uniform distribution of economic activity across the three parts of the Ile-de-France region at the end o f the study period, with each ring containing about one third o f total metropolitan employment.

However, this general spatial pattern varies for individual sectors. Over the 1978-1997 period, the process o f suburbanization of extensive land-use activities (industry, high-tech industry, construction and wholesale trade) and population-service-oriented activities (consumer services and public services) largely benefited the outer ring. The former were pushed out to the periphery because this was the only area able to offer sufficient floor space at affordable prices for their large plants, whereas the latter moved out to the suburbs to serve the booming market that the increasing decentralization of population was steadily creating at that time.

Employment in information-dependent activities (FIRE services and business services) tended to spread to the inner ring, and slightly to the outer ring. Between 1978 and 1997, the inner ring's share of regional employment in these two sectors rose respectively from 16% to 28% and 26% to 39%. The corresponding figures for the outer ring were 7% to 12% and 14.5% to 23.5%. At the same time, the share o f employment o f the Paris metropolitan area fell from 77% to 60% in the FIRE services sector and from 60% to 37% in the business services sector. Thus, despite substantial losses in FIRE employment, Paris maintained its leadership for FIRE activity, but the inner ring overtook the region's central zone for business services.

One explanation for this spatial distribution of information-dependent activities could be that new information technologies have rendered them more footloose. However, the dynamics at work would only bear out this thesis if no new concentrations of information-dependent activities were observed in the suburban zones. Thus, further examination is required to determine to what extent the spatial pattern displays a dispersed or a polycentric form and to ascertain the role of producer services in this process.

As shown in table 3, the results of the identification o f employment poles indicate that, in 1997, the 34 employment centers identified concentrated 69% of total regional employment, whereas only 31% was dispersed over the remainder o f the Ile-de-France region. This suggests that the Ile-de-France region displays a polycentric spatial pattern rather than a dispersed spatial distribution of employment.

[Table 3 about here]

This concentration of employment in poles is even more pronounced for informationdependent activities than for the other seven sectors, as poles contained 87% of the region's total FIRE employment and 79% of total metropolitan business services employment at the end o f the study period.

An interesting feature is that producer services employment concentrates in poles in general, but also in a number o f selective poles. Indeed, although the share of total regional employment of the eight central employment poles was eroded between 1978 and 1997, those poles still concentrated 70% of total regional FIRE services employment and 56% o f total regional business services employment in 1997. The respective figures for the 14 primary poles are 15% and 21%, and for the 12 isolated poles 2.4% and 1.7%. These results are consistent with those o f [START_REF] Alvergne | Nouvelles centralités, nouvelles périphéries en Ile-de-France : les changements de logiques de localisation des services supérieurs [New centrality, new peripheries in the Ile-de-France: the changing location patterns of high-order services[END_REF] and [START_REF] Shearmur | Intra-metropolitan patterns o f high-order business service location: a comparative study o f seventeen sectors in Ile-de-France[END_REF] who used complementary indicators o f concentration and dispersion for the Ile-de-France study. They also highlight the predominant role of the central part o f Paris in producer services employment.

However, o f all the central poles, only three of them, located west o f Pans, but adjacent to the inner beltway surrounding Paris, increased their share o f total regional employment in producer services, especially in business services: Issy-les-Moulineaux/Boulogne Billancourt (C6), Rueil/Suresnes/Nanterre (C7) and La Défense (C8). Conversely, the five central Paris poles, including the CBD, saw their share o f producer services total regional employment decline over the same period.

In addition to these central poles, three primary poles and one isolated pole, all located South of Paris, stand out as centers for business services: Ivry Pole (P12), 'La Plaine de Saclay' (P20), the 'Ville Nouvelle' of Saint-Quentin-en-Yvelines/Versailles (P21) and Plaisir (134). Elsewhere, six primary poles and one isolated pole diversified their economic base, in receiving business services, but without so far emerging as business services centers: All told, the results indicate that employment did indeed decentralize in the Ile-de-France region during the 1978-1997 period, and that producer services, and especially business services, acted a significant part in this process. As the suburbanization of these activities tended to reinforce a number of existing poles, this suggests that face-toface contacts, inducing these information-dependent activities to locate together in close proximity, have not yet been supplanted by new information technologies. However, even if some suburban poles have attracted substantial business services employment, we cannot yet conclude that these poles necessarily emerge as substitutes for the CBD. The next logical step is to determine whether the business services found in these poles are similar to those found in the CBD.

SPATIAL DYNAMICS OF PRODUCER SERVICES, 1978-1997

In spite of the traditionally higher rents associated with a CBD location, one o f the major reasons suggested in the recent literature for producer services agglomerating in such places is that clustering tends to minimize transaction costs. Specifically, the concentration o f firms facilitates the gathering and the transmission of non-standardized and highly complex information, and creates an information-rich environment [START_REF] Cappellin | Transaction costs and urban agglomeration[END_REF][START_REF] Romer | Endogenous technological change[END_REF][START_REF] Saxenian | Regional Advantage: Culture and Competition in Silicon Valley and Route 128[END_REF]. However, in the previous section, we found some evidence for the suburbanization of information-dependent activities during the 1978-1997 period in the Ile-de-France region and for new forms o f polarization in which these activities play a central role. Thus, to understand these phenomena, we feel it is important not to consider the producer services sector as a homogenous group of activities. Indeed, the literature on producer services points out that the spatial behavior o f these activities varies with the type o f service relationship concerned [START_REF] Daniels | Service Industries and the World Economy[END_REF][START_REF] Gadrey | Les relations de services dans le secteur marchand[END_REF][START_REF] Jouvaud | Vers une typologie des services aux entreprises selon leurs facteurs de localisation [Toward a typology o f producer services based on their location factors[END_REF].

Traditionally, the provision o f services is divided into four separate stages [START_REF] Vauthey | La modélisation des services intellectuels. Vendre et réaliser le service comme un produit [Modeling intellectual services[END_REF]: the design phase, the implementation phase, the delivery phase and the use phase. The phases during which the client and the service provider have to interact influence their need for proximity. This proximity constraint depends first o f all on the service features. These characteristics include the duration o f contact (service provided in part or completely at the client's location), the purpose of the contact (operational interactions involving a co-production relationship or contractual interactions involving a co-driving relationship) and its level o f standardization (if the service is standardized, contact with the client occurs only during the delivery and use phases). Second, the proximity constraint also depends on the frequency of the need. In this case, the more often the client uses the service, the greater the proximity constraint.

However, client proximity is not the sole factor influencing the location of producer services. Another specific feature of this economic sector is the existence of important intra-sectoral links between its different components: more than 70% of producer services firms' intermediate purchases are other producer services [START_REF] Jouvaud | Vers une typologie des services aux entreprises selon leurs facteurs de localisation [Toward a typology o f producer services based on their location factors[END_REF]. This feature contributes in part to the spatial clustering of complementary producer services firms. So, it is interesting to analyze whether the suburbanization process o f these activities has modified this spatial practice.

Our objective in this section is two-fold, then: first, we aim to examine whether differentiated spatial behaviors can be observed in the producer services sector. Secondly, we attempt to determine whether some specific clusters o f producer services emerge in those employment poles that were identified in the previous section as containing a substantial concentration o f these activities. In order to perform this part of our empirical analysis we elected to subdivide the FIRE and business service sectors into 16 employment categories: (1) Financial intermediaries (FI); ( 2 In order to identify differentiated spatial behavior of producer services activities, the respective sectoral specialization of the CBD, o f Paris non-CBD locations and of the two suburban rings, in each of the 15 employment categories, were examined for 1997. We compared the location quotient computed for each employment category in each zone with that associated with the producer service sector as a whole. An area was specialized, therefore, in a producer services category if its location quotient exceeded that o f all producer services (Table 4).

[Table 4 about here]

The results indicate that each zone is characterized by a specific cluster o f producer services. The Paris CBD stands out as a privileged location for high-order activities, such as financial intermediaries, insurance, financial and insurance auxiliaries, legal services, accounting services, but also for advertising and temporary work. The Paris non-CBD areas specialize in financial intermediaries, insurance, R&D, legal services, accounting services, opinion polls, architecture, temporary work and other producer services. The inner ring stands out from the other locations in being specialized in IT consultants, data processing, engineering, opinion polls, management consulting, advertising and other producer services. Locations in the outer ring are more attractive for real estate, engineering, R&D, opinion polls, architecture, temporary work and other producer services. These observations suggest that suburban locations emerge as complementary opportunities for location rather than as substitutes for the central location. In particular, the Paris CBD maintains its leadership in hyper-management functions, whereas technical services (IT consultants, engineering, data processing and R&D) prefer suburban locations. The Paris non-CBD zones emerge as intermediate areas specializing in high-order services and more standard services.

Examination of employment pole specialization in producer services employment provides insight into this analysis by ring. The new geography of activities and employment in the Ile-de-France region is characterized both by a polarization o f producer services in a small number of employment centers and by a different specialization of these centers. A clear diversification in the attraction o f territories is observed in the Ile-de-France region, corresponding to specific functions of the metropolitan production system. First, some poles receive office-based high-order services functions, like financial intermediaries, insurance, insurance or financial auxiliaries, legal services, accounting services, management consulting or advertising. These functions are concentrated in the CBD and in a few nearby suburban communes in the West, that is in 'La Défense'. The westward spread o f producer services from the CBD is also reported in previous studies of Ile-de-France [START_REF] Bekouche | La recomposition du centre économique parisien [The restructuring of the economic center in Ile-de-France[END_REF][START_REF] Alvergne | Nouvelles centralités, nouvelles périphéries en Ile-de-France : les changements de logiques de localisation des services supérieurs [New centrality, new peripheries in the Ile-de-France: the changing location patterns of high-order services[END_REF][START_REF] Shearmur | Intra-metropolitan patterns o f high-order business service location: a comparative study o f seventeen sectors in Ile-de-France[END_REF].

Nevertheless, this shift o f some commanding functions toward the western part o f the metropolitan region is not surprising, because it was encouraged by public policy. Indeed, all the office blocks built in Paris during the last 30 years have been located in Hauts-de-Seine, and especially in 'La Défense', in order to relieve congestion in central Paris. Thus, rather than suggesting a decline in the CBD's managerial economic role, this indicates an extension of office activities space requirements.

Second, certain other employment centers are business functional or managerial poles combining specializations in technical producer services (IT consultants, data processing and engineering) and productive functions, especially in the high-tech sector. An interesting feature is that the number of specialist technical producer services decreases with distance from Paris. Indeed, the Rueil/Nanterre/Suresnes and Issy-les-Moulineaux/Boulogne-Billancourt employment poles, surrounding the western part o f Paris's inner beltway, and the 'Ivry' employment pole, adjacent to the southern part o f Paris inner beltway, are specialized in three technical producer services: IT consultants, r)qta processing and engineering. Two poles located farther out in the south-western part of the metropolitan region stand out as specialized centers in two technical producer activities: IT consultants and engineering. Finally, the two 'Villes Nouvelles' o f Evry and Cergy-Pontoise are specialized exclusively in engineering.

Third, a number o f other poles are réception poles for transport functions and the wholesale trade, like Roissy and Orly airports, which are specialized in other producer services (security services, rental services, mailing services, packaging services, cleaning services, computer maintenance services...).

In fact, a more structured and more polarized employment geography emerged in 1997, indicating that face-to-face contacts, and thus tacit information, remain a key component in decisions about the location o f producer services. However, as tacit and codified information are complementary in the workings of producer services, we can justifiably wonder about the impact of telecommunication facilities on current producer services concentrations.

SUPPLY IN TELECOMMUNICATION FACILITIES AND THE POSSIBLE STRENGTHENING OF THE EXISTING CENTERS

The distinction between tacit information and codified information is a key to understanding the persistence o f the proximity constraint despite advances in information technologies. It also explains the suburbanization o f standard services, which rely largely on codified information.

However, this simplification is not entirely satisfactory and does not capture all the consequences of information technologies for the spatial organization of activities. In fact, the two types of information are complementary. First, the complementarity is organizational. For example, when a project involves several partners, this collaboration implies several sequences o f tacit and codified information exchange. Face-to-face contacts may be planned by phone or e-mail and those face-to-face contacts may be followed up by formal up-dates by phone, fax or e-mail [START_REF] Gaspar | Information technology and the future of cities[END_REF].

Second, the complementarity is decisional [START_REF] Guillain | Villes et échanges d'informations[END_REF]. The high-order services not only use tacit information but also codified information in order to reduce uncertainty. For example, firms look for macro-economic data about the economic climate, the market, economic policies, etc. This does not mean that tacit information is not important in decision-making. Indeed, in an increasingly complex economy, tacit information exchanges between agents may help in interpreting codified information. The financial market is a good example of this complementarity between the two types o f information. An increasing number o f agencies (like Reuters, Bloomberg, AP Dow Jones) now provide financial analyses, company accounts, economic reports, etc. A wealth o f codified information is available for the financial institutes, but face-to-face contacts are still useful when it comes to interpreting this information. 'Its complexity and uncertainty, [ . .. ] , has driven the denizens o f the City toward having to construct a more and more structured space o f face-to-face interaction/interpretation' [START_REF] Thrift | New urban eras and old technological fears: Reconfiguring the goodwill of electronic things[END_REF].

As a consequence, information-dependent activities locate in places where they can maximize the collection of tacit and codified information, that is, places with telecommunication equipment.

In Ile-de-France, firms have access to a well-developed network of telecommunication technologies. The territory is well covered and the network is modem with optical fibers allowing very high-volume information exchanges (IAURIF, 2001). First, this is because France Telecom was a state monopoly: the supply of telecommunication facilities was conducted in line with an equity-based strategy, that is to say France Telecom was compelled to satisfy demand from all potential users. Second, different programs in telecommunication research such as 'Francilienne des Télécommunications' and 'Réseau Récherche Ile-de-France', initiated by the authorities, helped improve the quality o f the network during the 1990s (IAURIF, 2001).

With the deregulation o f the telecommunication market in 1998, a number o f operators invested in Ile-de-France and this competition Tias resulted in uniform prices internationally (Rallet, 1999a). However, competition between operators could lead to a reinforcement of the polarization identified in section 4. Indeed, when we speak o f lowcost information exchanges by information technologies over long distances, we are referring to variable costs not fixed costs. Telecommunication technologies use complex physical infrastructures including real estate, which implies large investments in capital and innovation.

In a competitive environment, the priority for the telecommunication operators is to make their investments profitable. They therefore concentrate their services in places o f high demand [START_REF] Moss | Telecommunications, world cities, and urban policy[END_REF][START_REF] Sassen | The Global City[END_REF][START_REF] Daniels | Service Industries and the World Economy[END_REF][START_REF] Graham | Telecommunications and the City: Electronic Space, Urban Places[END_REF]. Our data cannot capture this phenomenon but this tendency seems to be going on today: 40 operators hold licenses to offer services in Ile-de-France. However, supply seems to be limited to the 'Petite Couronne' and more specifically to the area around 'la Défense' (Rallet, 1999a;IAURIF, 2001,). This may lead to a lock-in process in the choice o f localization because firms will always prefer places with modem telecommunication facilities, unless, for example, the authorities help operators to set-up in places where demand is lower by proposing joint investment projects.

CONCLUSION

Our study confirms that economic activity in the Paris metropolitan area is arranged in multiple centers, as it is in most cities in the industrialized world [START_REF] Anas | Urban spatial structure[END_REF]Shearmur and Coffey, 2000).

Our aim was to determine whether this process was the result o f advances in information technologies. It is clear that employment has decentralized from the CBD toward the suburbs. However, economic activity is not uniformly distributed throughout Ile-de-France. On the contrary, economic activity clusters in new employment poles, suggesting that face-to-face contacts are still important for information exchanges and remain a localization factor.

Analysis o f the sectoral composition reveals that the poles are dissimilar, specializing in different economic activities, especially in the case o f high-order services. The poles seem to be complements, rather than substitutes. Three tendencies are identified:

First, the center of Paris and the pole of 'La Défense' mainly attract financial intermediaries, insurance, financial and insurance auxiliaries, legal services, accounting services, management consulting and advertising. However, the two poles are not strictly in competition with one another even if high-order services employment seems to have shifted from the center toward 'La Défense', which therefore appears to be the new CBD of Paris. Indeed, the center of Paris is more highly specialized in the provision o f financial intermediaries, insurance, financial and insurance auxiliaries and legal services whereas 'La Défense' is more oriented toward the provision o f accounting services, advertising and especially management consulting. So, management functions still cluster in the center of Paris and its immediate western fringe, although new employment poles have emerged.

Second, 'La Défense' differs from central Paris in that it specializes in the hightech industry. This industry is concentrated in five major poles: in 'La Défense' and its immediate vicinity (Rueil/Surrennes/Nanterre), in the 'Ville Nouvelle' of Saint-Quentin-en-Yvelines/Versailles, in 'La Plaine de Saclay' and in the Ivry pole, and to a lesser extent, in the 'Villes Nouvelles' of Cergy and Evry. Engineering and IT consultants seem to be attracted by this high-tech environment even if IT consultants are not found in Evry.

Third, the two airports are specialized in logistics (transport and wholesale trade) and in ordinary services (security services, cleaning services, rental services, mailing services, packaging services, computer maintenance). Roissy airport is characterized by the presence of temporary work agencies and management consultancies, which may be because Roissy is the newer of the airports and handles more traffic than Orly.

This particular distribution of high order services in different poles suggests that high order services are not a homogeneous sector with uniform needs o f information, a point that is not considered in Ogawa and Fujita's models. As a consequence, not all services have incentives to be located in close geographic proximity to all the high order services. The geographical proximity between certain categories o f high order services seems to be more important than their proximity to all producer services. For example, financial services are more sensitive to locations close to accounting and legal services than to engineering services because o f strong informational complementarity between these activities and more frequent face-to-face contacts (LAURIF, 1998).

The fact that the poles are located close to the RER-SNCF lines and to the highways into the Ile-de-France reinforces this hypothesis. A similar situation is observed in North American cities (Coffey and Shearmur, 2000). A relative specialization of the centers may be considered with cluster o f activities, which present strong informational complementarity and frequent face-to-face encounters. The activities located in any given center may maintain ties with other centers, owing to less important informational complementarity and reduced need for face-to-face contacts.

In this context, information technologies may play an indirect role in the localization o f high order services. High order services will prefer centers with a good network o f telecommunication facilities and with real estate infrastructures adapted to the installation of these telecommunication technologies [START_REF] Longcore | Information technology and downtown restructuring: The case of New York City's financial district[END_REF]. The development o f employment centers in 'La Défense' and in the 'Villes Nouvelles' may reflect this process. The two regional plans in 1965 and 1994, designed to reduce the excessive growth of Paris by proposing new office space in 'La Défense' and in the 'Villes Nouvelles', influenced the pattern of suburbanization in Ile-de-France. Today 'La Défense' and most of the 'Villes Nouvelles' appear to be dynamic centers, offering good quality office facilities. This further suggests that public policies may have an effect on urban structure, which Shearmur and Coffey (2000) claim account for the differences in the patterns observed in Canadian cities.

I .

  ) High Tech Industry; (3) Construction; (4) Transport, Utilities and Communications (TUC); (5) Wholesale trade; (6) Consumer Services (CS); (7) Finance, Insurance and Real Estate (FIRE); (8) Business Services (BS) and (9) Public Services (PS).

  located North of Paris are La Plaine Saint-Denis (P9), Roissy airport (PI 8) and the 'Ville Nouvelle' of Cergy-Pontoise (P26); South o f Paris are the 'Ville Nouvelle' Eviy (P22), Etampes (133), and Orly airport (P I9); and finally, East of Paris are two employment poles belonging to the 'Ville Nouvelle' o f Mame-la-Vallée, Noisy-le-Grand (PI 5) andNoisiel (117).

  ) Insurance; (3) Insurance and Financial Auxiliaries (F&I Auxiliaries); (4) Real Estate; (5) IT Consultants; (6) Data Processing; (7) Engineering; (8) R&D; (9) Legal Services; (10) Accounting Services; (11) Opinion Polls; (12) Management Consulting; (13) Architecture; (14) Advertising; (15) Temporary Work and (16) Other producer services.

Fig. 1 .Fig. 2 .Fig. 3 .

 123 Fig. 1. Rings geography in Ile-de-France

TABLE 3 .-REGIONAL EMPLOYMENT SHARE BY POLE

 3

		Total central poles	Total primary poles	Total isolated poles	Rest of Ile-de-France	______ Total poles
		1978	1997	1978	1997	1978	1997	1978	1997	1978	1997
	Industry	41.13%	32.85%	25.70%	25.50%	6.26%	6.86%	26.91%	34.79%	73.09%	65.21%
	HT Industry 39.65%	27.11%	25.07%	31.09%	2.1 1 %	3.31%	33.17%	38.49%	66.83%	61.51%
	Construction 55.65%	24.07%	26.12%	23.14%	1.60%	2.58%	16.63%	50.21%	83.37%	49.79%
	TUC	34.99%	40.75%	21.75%	30.76%	2.56%	1.72%	40.70%	26.77%	59.30%	73.23%
	Wholesale	49.32%	33.15%	23.42%	31.90%	1.46%	1.46%	25.79%	33.48%	74.21%	66.52%
	CS	53.47%	47.63%	16.30%	17.08%	2.47%	3.55%	27.77%	31.75%	72.23%	68.25%
	FIRE	82.48%	70.39%	7.50%	14.90%	1.34%	2.39%	8.68%	12.31%	91.32%	87.69%
	BS	70.90%	56.01%	11.90%	21.39%	1.44%	1.70%	15.76%	20.90%	84.24%	79.09%
	PS	44,00%	37.01%	20.44%	23.69%	3.5%	4.05%	32.07%	35.25%	67.93%	64.75%
	Total	50.23%	42.86%	20.18%	23.43%	2.72%	3.06%	26.88%	30.65%	73.12%	69.35%

TABLE 4

 4

		.-LOCATION QUOTIENTS BY ZONE IN 1997
		CBD	Paris non-CBD Inner ring	Outer ring
	m	3,45	1,02	0,76	0,49
	Insurance	4,22	1,06	0,80	0,18
	F&I Auxiliaries	4,43	0,72	0,79	0,37
	Real Estate	1,80	0,99	0,98	0,78
	IT consultants	1,14	0,89	1,40	0,57
	Data processing	0,94	0,86	1,56	0,47
	Engineering	0,88	0,65	1,23	1,02
	R&D	0,27	1,15	0,91	1,22
	Legal services	3,25	1,45	0,49	0,56
	Accounting services	2,57	1,06	0,91	0,57
	Opinion polls	1,60	1,03	1,04	0,75
	Management consulting	1,82	0,76	1,23	0,65
	Architecture	0,94	2,00	0,66	0,69
	Advertising	2,06	0,92	1,30	0,38
	Temporary work	2,50	m	0,71	0,71
	Other producer services	1,03	1,09	1,05	0,87
	Total PS	1,99	0,99	1,02	0,67

Hauts-de-Seine, Seine-Saint-Denis and Val-de-Mame

Seine-et-Mame, Yvelines, Essonne and Val-d'Oise