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Microeconomics is the study of the behaviour of individuals and small impacting organisations in making decisions on the allocation of limited resources. The modern field of microeconomics arose as an effort of neoclassical economics school of thought to put economic ideas into mathematical mode. ==Traditional marginalism== An early attempt was made by Antoine Augustine Cournot in ''Researches on the Mathematical Principles of the Theory of Wealth''〔A. Cournot, Researches into the mathematical principles of the theory of wealth, 1838 http://archive.org/details/researchesintom00fishgoog〕 (1838) in describing a spring water duopoly that now bears his name. Later, William Stanley Jevons's ''Theory of Political Economy''〔S. Jevon, ''The Theory of Political Economy'',1871 http://www.econlib.org/library/YPDBooks/Jevons/jvnPE.html〕 (1871), Carl Menger's Principles of Economics〔C.Menger,Principles of Economics, 1871 https://mises.org/etexts/menger/principles.asp〕 (1871), and Léon Walras's ''Elements of Pure Economics: Or the theory of social wealth'' (1874–77)〔Leon Walras, Elements of Pure Economics, 1874 http://books.google.it/books/about/Elements_of_Pure_Economics.html?id=hwjRD3z0Qy4C&redir_esc=y〕 gave way to what was called the Marginal Revolution. Some common ideas behind those works were models or arguments characterised by rational economic agents maximising utility under a budget constrain. This arose as a necessity of arguing against the labour theory of value associated with classical economists such as Adam Smith, David Ricardo and Karl Marx. Walras also went as far as developing the concept of general equilibrium of an economy. Alfred Marshall's textbook, ''Principles of Economics''〔A. Marshall, Principles of Economics, 1890 http://www.econlib.org/library/Marshall/marP.html〕 was published in 1890 and became the dominant textbook in England for a generation. His main point was that Jevons went too far in emphasising utility as an attempt to explain prices over costs of production. In the book he writes: In the same appendix〔A.Marshall, Principles of Economics, 1890, APPENDIX I:RICARDO'S THEORY OF VALUE http://www.econlib.org/library/Marshall/marP64.html〕 he further states: Marshall's idea of solving the controversy was that the demand curve could be derived by aggregating individual consumer demand curves, which were themselves based on the consumer problem of maximising utility. The supply curve could be derived by superimposing a representative firm supply curves for the factors of production and then market equilibrium would be given by the intersection of demand and supply curves. He also introduced the notion of different market periods: mainly short run and long run. This set of ideas gave way to what economists call perfect competition, now found in the standard microeconomics texts, even though Marshall himself had stated:〔A.Marshall, Principles of Economics, 1890, BOOK VI, CHAPTER II: PRELIMINARY SURVEY OF DISTRIBUTION, CONTINUED. http://www.econlib.org/library/Marshall/marP44.html#Bk.VI,Ch.II〕 An early formulation of the concept of production functions is due to Johann Heinrich von Thünen, which presented an exponential version of it. The standard Cobb–Douglas production function found in microeconomics textbooks refers to a collaborative paper between Charles Cobb and Paul Douglas published in 1928 in which they analysed U.S. manufacturing data using this function as the basis of a regression analysis for estimating the relationship between inputs (labour and capital) and output (product): this discussion takes place through the concept of marginal productivity. The mathematical form of the Cobb–Douglas function can be found in the prior work of Wicksell, Thünen, and Turgot. Jacob Viner presented an early procedure for constructing cost curves in his “Cost Curves and Supply Curves” (1931),〔 Reprinted in 〕 the paper was an attempt to reconcile two streams of thought when dealing with this issue at the time: the idea that supplies of factors of production were given and independent of rate of remuneration (Austrian School) or dependent on rate of remuneration (English School, that is followers of Marshall). Viner argued that, “The differences between the two schools would not affect qualitatively the character of the findings,” more specifically, “...that this concern is not of sufficient importance to bring about any change in the prices of the factors as a result of a change in its output.” In Viner's terminology—now considered standard—the ''short run'' is a period long enough to permit any desired output change that is technologically possible without altering the scale of the plant—but is not long enough to adjust the scale of the plant. He arbitrarily assumes that all factors can, for the short run, be classified in two groups: those necessarily fixed in amount, and those freely variable. ''Scale of plant'' is the size of the group of factors that are fixed in amount in the short-run, and each scale is quantitatively indicated by the amount of output that can be produced at the lowest average cost possible at that scale. Costs associated with the fixed factors are ''fixed costs''. Those associated with the variable factors are ''direct costs''. Note that fixed costs are fixed only in their aggregate amounts, and vary with output in their amount per unit, while direct costs vary in their aggregate amount as output varies, as well as in their amount per unit. The spreading of overhead is therefore a short-run phenomenon and not to be confused with the long-run. He explains that if the law of diminishing returns holds that output per unit of variable factor falls as total output rises, and that if the prices of the factors remain constant—then average direct costs increase with output. Also, if atomistic competition prevails—that is, the individual firm output won't affect product prices—then the individual firm short-run supply curve equals the short run marginal cost curve. In the long run, the supply curve for industry can be constructed by summing individual marginal cost curves abscissas. He also explains that: *Internal economies of scale are primarily a long-run phenomenon and are due either to reductions in the technical coefficients of production (technical economies=increasing productivity by improved organisation or methods of production) or to discounts resulting from larger size (pecuniary economies). *Internal diseconomies of scale can be avoided by increasing industry output by increasing the number of plants without increasing the scale of the plant. *External economies of scale are also either technical or pecuniary, but in this case are due to the aggregate behaviour of the industry, and refer to the size of output of the industry as a whole. *External diseconomies of scale may occur if as industry output rises the unit price of factors and materials rises as well due to increasing competition for inputs with other industries. It should be made clear that these long-run results only hold if producer are rational actors, that is able to optimise their production so as to have an ''optimal scale of plant''. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Evolution of microeconomics」の詳細全文を読む スポンサード リンク
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