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An ''aggregate'' in economics is a summary measure describing a market or economy. The aggregation problem refers to the difficulty of treating an empirical or theoretical aggregate as if it reacted like a less-aggregated measure, say, about behavior of an individual agent as described in general microeconomic theory.〔Franklin M. Fisher (1987). "aggregation problem," ''The New Palgrave: A Dictionary of Economics'', v. 1, p. 54. (53-55. )〕 Examples of aggregates in micro- and macroeconomics relative to less aggregated counterparts are: * Food vs. apples * Price level and real GDP vs. the price and quantity of apples * Capital stock vs. the value of computers of a certain type and the value of steam shovels * Money supply vs. paper currency * General unemployment rate vs. the unemployment rate of civil engineers Standard theory uses simple assumptions to derive general, and commonly accepted, results such as the law of demand to explain market behavior. An example is the abstraction of a composite good. It considers the price of one good changing proportionately to the composite good, that is, all other goods. If this assumption is violated and the agents are subject to aggregated utility functions, restrictions on the latter are necessary to yield the law of demand. The aggregation problem emphasizes: * How broad such restrictions are in microeconomics * Use of broad factor inputs ("labor" and "capital"), real "output", and "investment", as if there was only a single such aggregate is without a solid foundation for rigorously deriving analytical results. Franklin Fisher notes that this has not dissuaded macroeconomists from continuing to use such concepts.〔Franklin M. Fisher (1987). "aggregation problem," ''The New Palgrave: A Dictionary of Economics'', v. 1, p. 55.〕 ==Aggregate consumer demand curve== The aggregate consumer demand curve is the summation of the individual consumer demand curves. The aggregation process preserves only two characteristics of individual consumer preference theory—continuity and homogeneity. Aggregation introduces three additional non-price determinants of demand: * Number of consumers * Distribution of tastes among the consumers * Distribution of incomes among consumers of different taste Thus if the population of consumers increases, ceteris paribus the demand curve will shift out; if the proportion of consumers with a strong preference for a good increases, ceteris paribus the demand for that good will change. Finally, if the distribution of income changes in favor of consumers who prefer the good in question, the demand will shift out. It is important to remember that factors that affect individual demand can also affect aggregate demand. However, net effects must be considered. 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「aggregation problem」の詳細全文を読む スポンサード リンク
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