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David Ricardo

David Ricardo (18 April 1772 – 11 September 1823) was a British political economist, politician, and member of the Parliament of Great Britain and Ireland. He is recognized as one of the most influential classical economists, alongside figures such as Thomas Malthus, Adam Smith and James Mill.

Ricardo was born in London as the third surviving child of a successful stockbroker and his wife. He came from a Sephardic Jewish family of Portuguese origin. At 21, he eloped with a Quaker and converted to Unitarianism, causing estrangement from his family. He made his fortune financing government borrowing and later retired to an estate in Gloucestershire. Ricardo served as High Sheriff of Gloucestershire and bought a seat in Parliament as an earnest reformer. He was friends with prominent figures like James Mill, Jeremy Bentham, and Thomas Malthus, engaging in debates over various topics. Ricardo was also a member of The Geological Society, and his youngest sister was an author.

As MP for Portarlington, Ricardo advocated for liberal political movements and reforms, including free trade, parliamentary reform, and criminal law reform. He believed free trade increased the well-being of people by making goods more affordable. Ricardo notably opposed the Corn Laws, which he saw as barriers to economic growth. His friend John Louis Mallett described Ricardo's conviction in his beliefs, though he expressed doubts about Ricardo's disregard for experience and practice. Ricardo died at 51 from an ear infection that led to septicaemia (sepsis). He left behind a considerable fortune and a lasting legacy, with his free trade views eventually becoming public policy in Britain.

Ricardo wrote his first economics article at age 37, advocating for a reduction in the note-issuing of the Bank of England. He was also an abolitionist and believed in the autonomy of a central bank as the issuer of money. Ricardo worked on fixing issues in Adam Smith's Labour Theory of Value, stating that the value of a commodity depends on the labour necessary for its production. He contributed to the development of theories of rent, wages, and profits, defining rent as the difference between the produce obtained by employing equal quantities of capital and labour. Ricardo's Theory of Profit posited that as real wages increase, real profits decrease due to the revenue split between profits and wages.

Ricardian theory of international trade challenges the mercantilism concept of accumulating gold or silver by promoting industry specialization and free trade. Ricardo introduced the concept of "comparative advantage," suggesting that nations should concentrate resources only in industries where they have the greatest efficiency of production relative to their own alternative uses of resources. He argued that international trade is always beneficial, even if one country is more competitive in every area than its trading counterpart. Ricardo opposed protectionism for national economies and was concerned about the short-term impact of technological change on labour.

Personal life
Born in London, England, Ricardo was the third surviving of the 17 children of successful stockbroker Abraham Israel Ricardo (1733?–1812) and Abigail (1753–1801), daughter of Abraham Delvalle (also "del Valle"), of a respectable Sephardic Jewish family that had been settled in England for three generations as "small but prosperous" tobacco and snuff merchants, and had obtained British citizenship. Abigail's sister, Rebecca, was wife of the engraver Wilson Lowry, and mother of the engraver Joseph Wilson Lowry and the geologist, mineralogist, and author Delvalle Lowry. The Ricardo family were Sephardic Jews of Portuguese origin who had recently relocated from the Dutch Republic. Ricardo began working with his father at the age of 14. At the age of 21 Ricardo eloped with a Quaker, Priscilla Anne Wilkinson, and, against his father's wishes, converted to Unitarianism. This religious difference resulted in estrangement from his family, and he was led to adopt a position of independence. His father disowned him and his mother apparently never spoke to him again.

Following this estrangement he went into business for himself with the support of Lubbocks and Forster, an eminent banking house. He made the bulk of his fortune by profitably financing Government borrowing. There is a story that he made his fortune as a result of speculation on the outcome of the Battle of Waterloo: The Sunday Times reported in Ricardo's obituary, published on 14 September 1823, that during the battle Ricardo "netted upwards of a million sterling", a huge sum at the time, and this was later popularised by the economist Paul Samuelson; in reality Ricardo was already very rich and in June 1815 sold his latest government stock before the result of the battle was known in London, so missing half of the rise.

He retired, and subsequently purchased Gatcombe Park, an estate in Gloucestershire, and retired to the country. He was appointed High Sheriff of Gloucestershire for 1818–19. In August 1818 he bought Lord Portarlingtons' seat in Parliament for £4,000, as part of the terms of a loan of £25,000. His record in Parliament was that of an earnest reformer. He held the seat until his death five years later.

Ricardo was a close friend of James Mill. Other notable friends included Jeremy Bentham and Thomas Malthus, with whom Ricardo had a considerable debate (in correspondence) over such things as the role of landowners in a society. He also was a member of Malthus' Political Economy Club, and a member of the King of Clubs. He was one of the original members of The Geological Society. His youngest sister was author Sarah Ricardo-Porter (e.g., Conversations in Arithmetic).

Parliamentary record
As MP for Portarlington, Ricardo voted with the opposition in support of liberal political movements in Naples and Sicily, and for inquiry into the administration of justice in Tobago. He divided for (voted for) repeal of the Blasphemous and Seditious Libels Act; then for inquiry into the Peterloo massacre; and, in 1821, for abolition of the death penalty for forgery.

He adamantly supported free trade. In 1821 he voted against renewal of the sugar duties, and objected to the higher duty on East Indian as opposed to West Indian produce. He opposed the timber duties. He voted silently for parliamentary reform and in 1822 spoke in its favour at the Westminster anniversary reform dinner; and again voted for criminal law reform.

Ricardo believed that increasing imports by free trade boosted the wellbeing of mankind by increasing the amount of goods cheaply available for subsistence and consumption. He was said to have "possessed an extraordinary quickness in perceiving in the turns of the market any accidental difference which might arise between the relative price of different stocks". And he grew his wealth dealing in securities during the Revolutionary and Napoleonic wars.

As the Napoleonic Wars waged on, Ricardo developed a disdain for the Corn Laws imposed by the British to encourage exports. Notably, government intervention in the grain trade can be traced as far back as the 1400s; and thereafter trade was controlled, regulated, and taxed. Meanwhile, England developed a capitalist economy involving workers and landlords generating and consuming incomes and capital accumulations that depended entirely on capitalists’ profits, and these key economic elements were under perpetual pressure during the eighteenth and early nineteenth centuries.

Political reform was needed as agricultural output was struggling to keep pace with population growth. The Corn Laws imposed barriers to imports that increased subsistence/consumption costs and triggered demand for higher wages. Higher wages reduced profits for agricultural producers, and had the immediate effects of reducing capital investments and slowing the growth of a nation's economy. Rising rents, attributed by Ricardo to the Corn Laws, came at the expense of the economic profits of nations. For David Ricardo, free trade was ever the answer; he envisioned Britain as importing agriculture products in exchange for exporting manufactured goods. Eventually, after his death, the interventionist laws were repealed, and his free trade views became public policy in Britain.

Of David Ricardo, his friend John Louis Mallett commented: " … he meets you upon every subject that he has studied with a mind made up, and opinions in the nature of mathematical truths. He spoke of parliamentary reform and ballot as a man who would bring such things about, and destroy the existing system tomorrow, if it were in his power, and without the slightest doubt on the result … It is this very quality of the man’s mind, his entire disregard of experience and practice, which makes me doubtful of his opinions on political economy."

Death and legacy
Ten years after retiring and four years after entering Parliament, Ricardo died from an infection of the middle ear that spread into his brain and induced septicaemia. He was 51.

He and his wife Priscilla had eight children together including Osman Ricardo (1795–1881; MP for Worcester 1847–1865), David Ricardo (1803–1864, MP for Stroud 1832–1833) and Mortimer Ricardo, who served as an officer in the Life Guards and was a deputy lieutenant for Oxfordshire.

Ricardo is buried in an ornate grave in the churchyard of Saint Nicholas in Hardenhuish, now a suburb of Chippenham, Wiltshire. At the time of his death his assets were estimated at £675,000–£775,000.

Ideas
Ricardo wrote his first economics article at 37, firstly in The Morning Chronicle advocating reduction in the note-issuing of the Bank of England and then publishing The High Price of Bullion, a Proof of the Depreciation of Bank Notes in 1810.

He was also an abolitionist, speaking at a meeting of the Court of the East India Company in March 1823, where he said he regarded slavery as a stain on the character of the nation.

Banking
Adam Smith argued that free commercial banking, such as the banking system in Scotland which had no central bank when Wealth of Nations was written in 1776, was favourable to economic growth. Writing just a few decades later, Ricardo argued for a central bank, a cause that was taken up by his students, including John Stuart Mill, who was known to favour the laissez-faire policies in every place but banking.

Ricardo wrote the Plan for the Establishment of a National Bank (published posthumously in 1824), which argued for the autonomy of the central bank as the issuer of money.

Ricardo proposed that a ratio of gold and Treasury bills, and a fixed claim (asset) against the government, would secure the central bank's liquidity:

"The public, or the Government on behalf of the public, is indebted to the Bank in a sum of money larger than the whole amount of Bank notes in circulation; for the Government not only owes the Bank fifteen million, its original capital, which is lent at 3 per cent. interest, but also many more millions which are advanced on Exchequer bills, on half-pay and pension annuities, and on other securities. It is evident, therefore, that if the Government itself were to be the sole issuer of paper money instead of borrowing it of the Bank, the only difference would be with respect to the interest: the Bank would no longer receive interest and the Government would no longer pay it; but all other classes in the community would be exactly in the same position in which they now stand."

Ricardo was a man of many trades, economically and financially speaking. Ricardo was able to recognize and identify the problem presented through banking within regulations and debauched standards of approval at certain times. Ricardo knew that banks in rural areas as well as the Bank of England had increased note lending and overall lending in 1810. Through this, Ricardo proved subsequent changes in price level through the market was also affected and thus new regulations needed to be made available. Furthermore, Ricardo was able to understand and distinguish the socioeconomic makeup that created and established parameters around different classes within the economy. Ricardo advocated for the productive powers of labour to be held in high concern as the most influential of devices that played a role in the progression of the American Economy along with others. In addition, Ricardo made notable advancements in the concept build involving reactions in the open market when considering banking altercations, stock investments, or other considerable impacting events. Ricardo wanted to establish a firm ground between the bank and the control over monetary policy because there was power within the banking system that Ricardo believed needed to be considered carefully. In 1816, Ricardo said “In the present state of the law, they have the power, without any control whatever, of increasing or reducing the circulation in any degree they may think proper: a power which should neither be entrusted to the State itself, nor to anybody in it; as there can be no security for the uniformity in the value of the currency, when its augmentation or diminution depends solely on the will of the issuers.” Ricardo felt the circulation of money and the decision behind how much is available at any time should not be entrusted to either the State, or any individual. Ricardo argued for the most even distribution possible with the highest control readily available.

Value theory
David Ricardo worked to fix the issues he felt were most concerning with Adam Smith’s Labour Theory of Value. Both men worked with the assumption that land, labour, and capital were the three basic factors of production. However, Smith narrowed in on labour as the determinant of value. Ricardo believes that with production having three factors it is impossible for only one of them to determine value on its own. Ricardo illustrates his point by adapting Smith's deer beaver analogy to show that even when labour is the only factor of production the hardship and tools of the labour will drive a wedge in the relative value of the good. Due to his criticisms of the Labour Theory of Value George Stigler called his theory a "93% labor theory of value".

Ricardo's most famous work is his Principles of Political Economy and Taxation (1817). He advanced a labour theory of value:

"The value of a commodity, or the quantity of any other commodity for which it will exchange, depends on the relative quantity of labour which is necessary for its production, and not on the greater or less compensation which is paid for that labour."

Ricardo's note to Section VI:

"Mr. Malthus appears to think that it is a part of my doctrine, that the cost and value of a thing be the same;—it is, if he means by cost, 'cost of production' including profit."

Rent
Ricardo contributed to the development of theories of rent, wages, and profits. He defined rent as "the difference between the produce obtained by the employment of two equal quantities of capital and labour." Ricardo believed that the process of economic development, which increased land use and eventually led to the cultivation of poorer land, principally benefited landowners. According to Ricardo, such premium over "real social value" that is reaped due to ownership constitutes value to an individual but is at best a paper monetary return to "society". The portion of such purely individual benefit that accrues to scarce resources Ricardo labels "rent".

In particular, Ricardo postulates that rent is a result of increased populations which results in assets growing scarce and in some cases diminished returns of which were once abundant. Ricardo breaks down this premise by first supposing there are three fields of land - No. 1, 2, 3, - to yield corn, with an equal employment of capital and labour. Initially land No.1 is cultivated and is very productive as measured through the abundant surplus. Over time this abundant surplus becomes diminished as the result of an increase in population, which subsequently creates an increased demand for food. The less desired land, No.2, must now be cultivated and eventually so must land No.3 and so on and so forth. For Ricardo each new cultivated results in diminished surplus as the quality of land fails to yield the equal of that before it. In light of such diminishing surplus landowners see opportunities to charge rent as a means to compensate for the loss of returns on output.

Ricardo's theories of wages and profits
In his Theory of Profit, Ricardo stated that as real wages increase, real profits decrease because the revenue from the sale of manufactured goods is split between profits and wages. He said in his Essay on Profits, "Profits depend on high or low wages, wages on the price of necessaries, and the price of necessaries chiefly on the price of food."

Ricardian theory of international trade
Between 1500 and 1750 most economists advocated mercantilism, which promoted the idea of international trade for the purpose of earning bullion by running a trade surplus with other countries. Ricardo challenged the idea that the purpose of trade was merely to accumulate gold or silver. With "comparative advantage" Ricardo argued in favour of industry specialisation and free trade. He suggested that industry specialization combined with free international trade always produces positive results. This theory expanded on the concept of absolute advantage.

Ricardo suggested that there is mutual national benefit from trade even if one country is more competitive in every area than its trading counterpart and that a nation should concentrate resources only in industries where it has a comparative advantage, that is in those industries in which it has the greatest efficiency of production relative to its own alternative uses of resources, rather than industries where it holds a competitive edge compared to rival nations. Ricardo suggested that national industries which were, in fact, mildly profitable and marginally internationally competitive should be jettisoned in favour of the industries that made the best use of limited resources—the assumption being that subsequent economic growth due to better resource use would more than offset any short-run economic dislocation which would result from closing mildly profitable and marginally competitive national industries.

Ricardo attempted to prove theoretically that international trade is always beneficial. Paul Samuelson called the numbers used in Ricardo's example dealing with trade between England and Portugal the "four magic numbers". "In spite of the fact that the Portuguese could produce both cloth and wine with less amount of labour, Ricardo suggested that both countries would benefit from trade with each other".

As for recent extensions of Ricardian models, see Ricardian trade theory extensions.

Comparative advantage
Ricardo's theory of international trade was reformulated by John Stuart Mill in 1844. The term "comparative advantage" was introduced by J. S. Mill and his contemporaries.

John Stuart Mill started a neoclassical turn of international trade theory, i.e. his formulation was inherited by Alfred Marshall and others, and has both contributed to the resurrection of the anti-Ricardian concept of law of supply and demand, and induced the arrival of neoclassical theory of value.

New interpretation
Ricardo's four magic numbers have long been interpreted as comparison of two ratios of labour (or other input in fixed supply) coefficients. This interpretation is now considered as overly simplistic by modern economists. The point was rediscovered by Roy J. Ruffin in 2002 and re-examined and explained in detail in Andrea Maneschi in 2004. The more flexible approach is now known as the new interpretation, despite having been previously mentioned by Piero Sraffa in 1930 and by Kenzo Yukizawa in 1974. The new interpretation affords a totally new reading of Ricardo's Principles of Political Economy and Taxation with regards to trade theory, although it does not change the mathematics of optimal resource allocation.

Protectionism
Like Adam Smith, Ricardo was an opponent of protectionism for national economies, especially for agriculture. He believed that the British "Corn Laws"—imposing tariffs on agricultural products—ensured that less-productive domestic land would be cultivated and rents would be driven up. Thus, profits would be directed toward landlords and away from the emerging industrial capitalists. Ricardo believed landlords tended to squander their wealth on luxuries, rather than invest. He believed the Corn Laws were leading to the stagnation of the British economy. In 1846, his nephew John Lewis Ricardo, MP for Stoke-upon-Trent, advocated free trade and the repeal of the Corn Laws.

Modern empirical analysis of the Corn Laws yields mixed results. Parliament repealed the Corn Laws in 1846.

Technological change
Ricardo was concerned about the impact of technological change on labour in the short-term. In 1821, he wrote that he had become "convinced that the substitution of machinery for human labour, is often very injurious to the interests of the class of labourers," and that "the opinion entertained by the labouring class, that the employment of machinery is frequently detrimental to their interests, is not founded on prejudice and error, but is conformable to the correct principles of political economy." Ricardo's idea of technological change is now formulated in a modern form.

Criticism of the Ricardian theory of trade
Ricardo himself was the first to recognize that comparative advantage is a domain-specific theory, meaning that it applies only when certain conditions are met. Ricardo noted that the theory applies only in situations where capital is immobile. Regarding his famous example, he wrote: it would undoubtedly be advantageous to the capitalists [and consumers] of England... [that] the wine and cloth should both be made in Portugal [and that] the capital and labour of England employed in making cloth should be removed to Portugal for that purpose.

Ricardo recognized that applying his theory in situations where capital was mobile would result in offshoring, and thereby economic decline and job loss. To correct for this, he argued that (i) "most men of property [will be] satisfied with a low rate of profits in their own country, rather than seek[ing] a more advantageous employment for their wealth in foreign nations", and (ii) capital was functionally immobile.

Ricardo's argument in favour of free trade has also been attacked by those who believe trade restriction can be necessary for the economic development of a nation. Utsa Patnaik claims that Ricardian theory of international trade contains a logical fallacy. Ricardo assumed that in both countries two goods are producible and actually are produced, but developed and underdeveloped countries often trade those goods which are not producible in their own country. In these cases, one cannot define which country has comparative advantage.

Critics also argue that Ricardo's theory of comparative advantage is flawed in that it assumes production is continuous and absolute. In the real world, events outside the realm of human control (e.g. natural disasters) can disrupt production. In this case, specialisation could cripple a country that depends on imports from foreign, naturally disrupted countries. For example, if an industrially based country trades its manufactured goods with an agrarian country in exchange for agricultural products, a natural disaster in the agricultural country (e.g. drought) may cause the industrially based country to starve.

As Joan Robinson pointed out, following the opening of free trade with England, Portugal endured centuries of economic underdevelopment: "the imposition of free trade on Portugal killed off a promising textile industry and left her with a slow-growing export market for wine, while for England, exports of cotton cloth led to accumulation, mechanisation and the whole spiralling growth of the industrial revolution". Robinson argued that Ricardo's example required that economies be in static equilibrium positions with full employment and that there could not be a trade deficit or a trade surplus. These conditions, she wrote, were not relevant to the real world. She also argued that Ricardo's math did not take into account that some countries may be at different levels of development and that this raised the prospect of 'unequal exchange' which might hamper a country's development, as we saw in the case of Portugal.

The development economist Ha-Joon Chang challenges the argument that free trade benefits every country: Ricardo’s theory is absolutely right—within its narrow confines. His theory correctly says that, accepting their current levels of technology as given, it is better for countries to specialize in things that they are relatively better at. One cannot argue with that. His theory fails when a country wants to acquire more advanced technologies—that is, when it wants to develop its economy. It takes time and experience to absorb new technologies, so technologically backward producers need a period of protection from international competition during this period of learning. Such protection is costly, because the country is giving up the chance to import better and cheaper products. However, it is a price that has to be paid if it wants to develop advanced industries. Ricardo’s theory is, thus seen, for those who accept the status quo but not for those who want to change it.

Ricardian equivalence
Another idea associated with Ricardo is Ricardian equivalence, an argument suggesting that in some circumstances a government's choice of how to pay for its spending (i.e., whether to use tax revenue or issue debt and run a deficit) might have no effect on the economy. This is due to the fact the public saves its excess money to pay for expected future tax increases that will be used to pay off the debt. Ricardo notes that the proposition is theoretically implied in the presence of intertemporal optimisation by rational taxpayers: but that since taxpayers do not act so rationally, the proposition fails to be true in practice. Thus, while the proposition bears his name, he does not seem to have believed it. Economist Robert Barro is responsible for its modern prominence.

Influence and intellectual legacy
David Ricardo's ideas had a tremendous influence on later developments in economics. US economists rank Ricardo as the second most influential economic thinker, behind Adam Smith, prior to the twentieth century.

Ricardian socialists
Ricardo's writings fascinated a number of early socialists in the 1820s, who thought his value theory had radical implications. They argued that, in view of labour theory of value, labour produces the entire product, and the profits capitalists get are a result of exploitations of workers. These include Thomas Hodgskin, William Thompson, John Francis Bray, and Percy Ravenstone.

Georgists
Georgists believe that rent, in the sense that Ricardo used, belongs to the community as a whole. Henry George was greatly influenced by Ricardo, and often cited him, including in his most famous work, Progress and Poverty from 1879. In the preface to the fourth edition he wrote: "What I have done in this book, if I have correctly solved the great problem I have sought to investigate, is, to unite the truth perceived by the school of Smith and Ricardo to the truth perceived by the school of Proudhon and Lasalle; to show that laissez faire (in its full true meaning) opens the way to a realization of the noble dreams of socialism; to identify social law with moral law, and to disprove ideas which in the minds of many cloud grand and elevating perceptions."

Neo-Ricardians
After the rise of the 'neoclassical' school, Ricardo's influence declined temporarily. It was Piero Sraffa, the editor of the Collected Works of David Ricardo and the author of seminal Production of Commodities by Means of Commodities, who resurrected Ricardo as the originator of another strand of economic thought, which was effaced with the arrival of the neoclassical school. The new interpretation of Ricardo and Sraffa's criticism against the marginal theory of value gave rise to a new school, now named neo-Ricardian or Sraffian school. Major contributors to this school include Luigi Pasinetti (1930–), Pierangelo Garegnani (1930–2011), Ian Steedman (1941–), Geoffrey Harcourt (1931–2021), Heinz Kurz (1946–), Neri Salvadori (1951–), Pier Paolo Saviotti (–) among others. See also Neo-Ricardianism. The Neo-Ricardian school is sometimes seen to be a component of Post-Keynesian economics.

Neo-Ricardian trade theory
Inspired by Piero Sraffa, a new strand of trade theory emerged and was named neo-Ricardian trade theory. The main contributors include Ian Steedman and Stanley Metcalfe. They have criticised neoclassical international trade theory, namely the Heckscher–Ohlin model on the basis that the notion of capital as primary factor has no method of measuring it before the determination of profit rate (thus trapped in a logical vicious circle). This was a second round of the Cambridge capital controversy, this time in the field of international trade. Depoortère and Ravix judge that neo-Ricardian contribution failed without giving effective impact on neoclassical trade theory, because it could not offer "a genuine alternative approach from a classical point of view."

Evolutionary growth theory
Several distinctive groups have sprung out of the neo-Ricardian school. One is the evolutionary growth theory, developed notably by Luigi Pasinetti, J.S. Metcalfe, Pier Paolo Saviotti, and Koen Frenken and others.

Pasinetti argued that the demand for any commodity came to stagnate and frequently decline, demand saturation occurs. Introduction of new commodities (goods and services) is necessary to avoid economic stagnation.

Contemporary theories
Ricardo's idea was even expanded to the case of continuum of goods by Dornbusch, Fischer, and Samuelson This formulation is employed for example by Matsuyama and others.

Ricardian trade theory ordinarily assumes that the labour is the unique input. This is a deficiency as intermediate goods occupies now a great part of international trade. The situation changed after the appearance of Yoshinori Shiozawa's work of 2007. He has succeeded to incorporate traded input goods in his model. His theory became more useful by the discovery of new definition of regular international values (a couple of wage rates for countries and prices for products), because it is not defined as the normal vector at a facet of world production possibility set, which is the set where all countries enjoy full employment. The new definition is given in Shiozawa and Fujimoto (2018) and in Shiozawa (2020). Shiozawa's theory of international values is now the unique theory of international trade that can treat unemployment and input trade in a general form.

Yeats found that 30% of world trade in manufacturing is intermediate inputs. Bardhan and Jafee found that intermediate inputs occupy 37 to 38% in the imports to the US for the years from 1992 to 1997, whereas the percentage of intrafirm trade grew from 43% in 1992 to 52% in 1997.

Unequal exchange
Chris Edward includes Emmanuel's unequal exchange theory among variations of neo-Ricardian trade theory. Arghiri Emmanuel argued that the Third World is poor because of the international exploitation of labour.

The unequal exchange theory of trade has been influential to the (new) dependency theory.

Publications
Ricardo's publications included:
 * The High Price of Bullion, a Proof of the Depreciation of Bank Notes (1810), which advocated the adoption of a metallic currency.
 * Essay on the Influence of a Low Price of Corn on the Profits of Stock (1815), which argued that repealing the Corn Laws would distribute more wealth to the productive members of society.
 * On the Principles of Political Economy and Taxation (1817), an analysis that concluded that land rent grows as population increases. It also clearly laid out the theory of comparative advantage, which argued that all nations could benefit from free trade, even if a nation was less efficient at producing all kinds of goods than its trading partners.

His works and writings were collected in (11 volumes)

title: David Ricardo


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Delphinus

Delphinus (Pronounced or ) is a small constellation in the Northern Celestial Hemisphere, close to the celestial equator. Its name is the Latin version for the Greek word for dolphin (δελφίς). It is one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations recognized by the International Astronomical Union. It is one of the smaller constellations, ranked 69th in size. Delphinus' five brightest stars form a distinctive asterism symbolizing a dolphin with four stars representing the body and one the tail. It is bordered (clockwise from north) by Vulpecula, Sagitta, Aquila, Aquarius, Equuleus and Pegasus.

Delphinus is a faint constellation with only two stars brighter than an apparent magnitude of 4, Beta Delphini (Rotanev) at magnitude 3.6 and Alpha Delphini (Sualocin) at magnitude 3.8.

Mythology
Delphinus is associated with two stories from Greek mythology.

According to myth, the first Greek god Poseidon wanted to marry Amphitrite, a beautiful nereid. However, wanting to protect her virginity, she fled to the Atlas mountains. Her suitor then sent out several searchers, among them a certain Delphinus. Delphinus accidentally stumbled upon her and was able to persuade Amphitrite to accept Poseidon's wooing. Out of gratitude the god placed the image of a dolphin among the stars.

The second story tells of the Greek poet Arion of Lesbos (7th century BC), who was saved by a dolphin. He was a court musician at the palace of Periander, ruler of Corinth. Arion had amassed a fortune during his travels to Sicily and Italy. On his way home from Tarentum his wealth caused the crew of his ship to conspire against him. Threatened with death, Arion asked to be granted a last wish which the crew granted: he wanted to sing a dirge. This he did, and while doing so, flung himself into the sea. There, he was rescued by a dolphin which had been charmed by Arion's music. The dolphin carried Arion to the coast of Greece and left.

In non-Western astronomy
In Chinese astronomy, the stars of Delphinus are located within the Black Tortoise of the North (北方玄武, Běi Fāng Xuán Wǔ).

In Polynesia, two cultures recognized Delphinus as a constellation. In Pukapuka, it was called Te Toloa and in the Tuamotus, it was called Te Uru-o-tiki.

In Hindu astrology, the Delphinus corresponds to the Nakshatra, or lunar mansion, of Dhanishta.

Characteristics
Delphinus is bordered by Vulpecula to the north, Sagitta to the northwest, Aquila to the west and southwest, Aquarius to the southeast, Equuleus to the east and Pegasus to the east. Covering 188.5 square degrees, corresponding to 0.457% of the sky, it ranks 69th of the 88 constellations in size. The three-letter abbreviation for the constellation, as adopted by the IAU in 1922, is "Del". The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of 14 segments. In the equatorial coordinate system, the right ascension coordinates of these borders lie between 20:14:14.1594 and 21:08:59.6073, while the declination coordinates are between +2.4021468° and +20.9399471°. The whole constellation is visible to observers north of latitude 69°S.

Features

Stars
Delphinus has two stars above fourth (apparent) magnitude; its brightest star is of magnitude 3.6. The main asterism in Delphinus is Job's Coffin, nearly a 45°-apex lozenge or diamond of the four brightest stars: Alpha, Beta, Gamma, and Delta Delphini. Delphinus is in a rich Milky Way star field. Alpha and Beta Delphini have 19th century names Sualocin and Rotanev, read backwards: Nicolaus Venator, the Latinized name of a Palermo Observatory director, Niccolò Cacciatore (d. 1841).

Alpha Delphini is a blue-white hued main sequence star of magnitude 3.8, 241 light-years from Earth. It is a spectroscopic binary. It is officially named Sualocin. The star has an absolute magnitude of -0.4.

Beta Delphini is officially called Rotanev. It was found to be a binary star in 1873. The gap between its close binary stars is visible from large amateur telescopes. To the unaided eye, it appears to be a white star of magnitude 3.6. It has a period of 27 years and is 97 light-years from Earth.

Gamma Delphini is a celebrated binary star among amateur astronomers. The primary is orange-gold of magnitude 4.3; the secondary is a light yellow star of magnitude 5.1. The pair form a true binary with an estimated orbital period of over 3,000 years. 125 light-years away, the two components are visible in a small amateur telescope. The secondary, also described as green, is 10 arcseconds from the primary. Struve 2725, called the "Ghost Double", is a pair that appears similar but dimmer. Its components of magnitudes 7.6 and 8.4 are separated by 6 arcseconds and are 15 arcminutes from Gamma Delphini itself. An unconfirmed exoplanet with a minimum mass of 0.7 Jupiter masses may orbit one of the stars.

Delta Delphini is a type A-type star of magnitude 4.43. It is a spectroscopic binary, and both stars are Delta Scuti variables.

Epsilon Delphini, Deneb Dulfim (lit. "tail [of the] Dolphin"), or Aldulfin, is a star of stellar class B6 III. Its magnitude is variable at around 4.03.

Zeta Delphini, an A3Va main-sequence star of magnitude 4.6, was in 2014 discovered to have a brown dwarf orbiting around it. Zeta Delphini B has a mass of 50±15.

Rho Aquilae at magnitude 4.94 is at about 150 light-years away. Due to its proper motion it has been in the (round-figure parameter) bounds of the constellation since 1992. It is an A-type main sequence star with a lower metallicity than the Sun.

HR Delphini was a nova that brightened to magnitude 3.5 in December 1967. It took an unusually long time for the nova to reach peak brightness which indicate that it barely satisfied the conditions for a thermonuclear runaway. Another nova by the name V339 Delphini was detected in 2013; it peaked at magnitude 4.3 and was the first nova observed to produce lithium.

Musica, also known by its Flamsteed designation 18 Delphini, is one of the five stars with known planets located in Delphinus. It has a spectral type of G6 III. Arion, the planet, is a very dense and massive planet with a mass at least 10.3 times greater than Jupiter. Arion was part of the first NameExoWorlds contest where the public got the opportunity to suggest names for exoplanets and their host stars.

Exoplanets
In 2024 the planet TOI-6883 b was discovered in the constellation Delphinus. It has a 16.249 day orbital period around its host star, a radius 1.08 times Jupiter's, and a mass 4.34 times Jupiter's. It was discovered from a single transit in TESS data and it was confirmed by a network of citizen scientists.

Deep-sky objects
Its rich Milky Way star field means many modestly deep-sky objects. NGC 6891 is a planetary nebula of magnitude 10.5; another is NGC 6905 or the Blue Flash Nebula. The Blue Flash Nebula shows broad emission lines. The central star in NGC 6905 has a spectral of WO2, meaning it is rich in oxygen.

NGC 6934 is a globular cluster of magnitude 9.75. It is about 52,000 light-years away from the Solar System. It is in the Shapley-Sawyer Concentration Class VIII and is thought to share a common origin with another globular cluster in Boötes. It has an intermediate metallicity for a globular cluster, but as of 2018 it has been poorly studied. At a distance of about 137,000 light-years, the globular cluster NGC 7006 is at the outer reaches of the galaxy. It is also fairly dim at magnitude 11.5 and is in Class I.

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title: Delphinus


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Disk storage

Disk storage (also sometimes called drive storage) is a data storage mechanism based on a rotating disk. The recording employs various electronic, magnetic, optical, or mechanical changes to the disk's surface layer. A disk drive is a device implementing such a storage mechanism. Notable types are hard disk drives (HDD), containing one or more non-removable rigid platters; the floppy disk drive (FDD) and its removable floppy disk; and various optical disc drives (ODD) and associated optical disc media.

(The spelling disk and disc are used interchangeably except where trademarks preclude one usage, e.g. the Compact Disc logo. The choice of a particular form is frequently historical, as in IBM's usage of the disk form beginning in 1956 with the "IBM 350 disk storage unit".)

Background
Audio information was originally recorded by analog methods (see Sound recording and reproduction). Similarly the first video disc used an analog recording method. In the music industry, analog recording has been mostly replaced by digital optical technology where the data is recorded in a digital format with optical information.

The first commercial digital disk storage device was the IBM 350 which shipped in 1956 as a part of the IBM 305 RAMAC computing system. The random-access, low-density storage of disks was developed to complement the already used sequential-access, high-density storage provided by tape drives using magnetic tape. Vigorous innovation in disk storage technology, coupled with less vigorous innovation in tape storage, has reduced the difference in acquisition cost per terabyte between disk storage and tape storage; however, the total cost of ownership of data on disk including power and management remains larger than that of tape.

Disk storage is now used in both computer storage and consumer electronic storage, e.g., audio CDs and video discs (VCD, DVD and Blu-ray).

Data on modern disks is stored in fixed length blocks, usually called sectors and varying in length from a few hundred to many thousands of bytes. Gross disk drive capacity is simply the number of disk surfaces times the number of blocks/surface times the number of bytes/block. In certain legacy IBM CKD drives the data was stored on magnetic disks with variable length blocks, called records; record length could vary on and between disks. Capacity decreased as record length decreased due to the necessary gaps between blocks.

Access methods
Digital disk drives are block storage devices. Each disk is divided into logical blocks (collection of sectors). Blocks are addressed using their logical block addresses (LBA). Read from or writing to disk happens at the granularity of blocks.

Originally the disk capacity was quite low and has been improved in one of several ways. Improvements in mechanical design and manufacture allowed smaller and more precise heads, meaning that more tracks could be stored on each of the disks. Advancements in data compression methods permitted more information to be stored in each of the individual sectors.

The drive stores data onto cylinders, heads, and sectors. The sectors unit is the smallest size of data to be stored in a hard disk drive and each file will have many sectors units assigned to it. The smallest entity in a CD is called a frame, which consists of 33 bytes and contains six complete 16-bit stereo samples (two bytes × two channels × six samples = 24 bytes). The other nine bytes consist of eight CIRC error-correction bytes and one subcode byte used for control and display.

The information is sent from the computer processor to the BIOS into a chip controlling the data transfer. This is then sent out to the hard drive via a multi-wire connector. Once the data is received onto the circuit board of the drive, they are translated and compressed into a format that the individual drive can use to store onto the disk itself. The data is then passed to a chip on the circuit board that controls the access to the drive. The drive is divided into sectors of data stored onto one of the sides of one of the internal disks. An HDD with two disks internally will typically store data on all four surfaces.

The hardware on the drive tells the actuator arm where it is to go for the relevant track and the compressed information is then sent down to the head which changes the physical properties, optically or magnetically for example, of each byte on the drive, thus storing the information. A file is not stored in a linear manner, rather, it is held in the best way for quickest retrieval.

Rotation speed and track layout
[[File:Comparison disk storage.svg|thumb|300px|Comparison of several forms of disk storage showing tracks (not-to-scale); green denotes start and red denotes end. Mechanically there are two different motions occurring inside the drive. One is the rotation of the disks inside the device. The other is the side-to-side motion of the head across the disk as it moves between tracks.
 * Some CD-R(W) and DVD-R(W)/DVD+R(W) recorders operate in ZCLV, CAA or CAV modes.]]

There are two types of disk rotation methods:
 * constant linear velocity (used mainly in optical storage) varies the rotational speed of the optical disc depending upon the position of the head, and
 * constant angular velocity (used in HDDs, standard FDDs, a few optical disc systems, and vinyl audio records) spins the media at one constant speed regardless of where the head is positioned.

Track positioning also follows two different methods across disk storage devices. Storage devices focused on holding computer data, e.g., HDDs, FDDs, Iomega zip drives, use concentric tracks to store data. During a sequential read or write operation, after the drive accesses all the sectors in a track it repositions the head(s) to the next track. This will cause a momentary delay in the flow of data between the device and the computer. In contrast, optical audio and video discs use a single spiral track that starts at the inner most point on the disc and flows continuously to the outer edge. When reading or writing data there is no need to stop the flow of data to switch tracks. This is similar to vinyl records except vinyl records started at the outer edge and spiraled in toward the center.

Interfaces
The disk drive interface is the mechanism/protocol of communication between the rest of the system and the disk drive itself. Storage devices intended for desktop and mobile computers typically use ATA (PATA) and SATA interfaces. Enterprise systems and high-end storage devices will typically use SCSI, SAS, and FC interfaces in addition to some use of SATA.

Basic terminology

 * Disk : Generally refers to magnetic media and devices.
 * Disc : Required by trademarks for certain optical media and devices.
 * Platter : An individual recording disk. A hard disk drive contains a set of platters. Developments in optical technology have led to multiple recording layers on DVDs.
 * Spindle : the spinning axle on which the platters are mounted.
 * Rotation : Platters rotate; two techniques are common:
 * Constant angular velocity (CAV) keeps the disk spinning at a fixed rate, measured in revolutions per minute (RPM). This means the heads cover more distance per unit of time on the outer tracks than on the inner tracks. This method is typical with computer hard drives.
 * Constant linear velocity (CLV) keeps the distance covered by the heads per unit time fixed. Thus the disk has to slow down as the arm moves to the outer tracks. This method is typical for CD drives.

 * Track : The circle of recorded data on a single recording surface of a platter.

 * Sector : A segment of a track
 * Low level formatting : Establishing the tracks and sectors.
 * Head : The device that reads and writes the information—magnetic or optical—on the disk surface.
 * Arm : The mechanical assembly that supports the head as it moves in and out.
 * Seek time : Time needed to move the head to a new position (specific track).
 * Rotational latency : Average time, once the arm is on the right track, before a head is over a desired sector.
 * Data transfer rate : The rate at which user data bits are transferred from or to the medium. Technically, this would more accurately be entitled the "gross" data transfer rate.

title: Disk storage