Долгосрочный и краткосрочный периоды в экономической теории

Concepts in economics
In economics, the long run is a theoretical concept in which all markets are in equilibrium, and all prices and quantities have fully adjusted and are in equilibrium. The long run contrasts with the short run, in which there are some constraints and markets are not fully in equilibrium. More specifically, in microeconomics there are no fixed factors of production in the long run, and there is enough time for adjustment so that there are no constraints preventing changing the output level by changing the capital stock or by entering or leaving an industry. This contrasts with the short run, where some factors are variable (dependent on the quantity produced) and others are fixed (paid once), constraining entry or exit from an industry. In macroeconomics, the long run is the period when the general price level, contractual wage rates, and expectations adjust fully to the state of the economy, in contrast to the short run when these variables may not fully adjust.

The differentiation between long run and short run economic models did not come into practice until 1890, with Alfred Marshall's publication of his work Principles of Economics. However, there is no hard and fast definition as to what is classified as "long" or "short" and mostly relies on the economic perspective being taken. Marshall's original introduction of long run and short run economics reflected the 'long period method' that was a common analysis used by classical political economists. However, early in the 1930s, dissatisfaction with a variety of the conclusions of Marshall's original theory led to methods of analysis and introduction of equilibrium notions. Classical political economists, neoclassical economists, Keynesian economists all have slightly different interpretations and explanations as to how short run and long run equilibriums are defined, reached, and what factors influence them. (maybe provide some examples of some specific influences?) Economic theory has employed the "long period technique" of analysis to examine how production, distribution, and accumulation take place within a market economy ever since its first appearance in the writings of the 18th century. According to classical political economists like Adam Smith, the "natural" or "average" rates of salaries, profits, and rent tend to become more uniform as a result of competition. Consequently, "market" prices, or observed prices, tend to gravitate toward their "natural" levels. In this case, according to the classical political economists, the divergence between a commodity's provide example of a commodity "market" and "natural" price is established by a disparity between the amount provided by producers and the "effective demand" for it. This gap between the "market" and "natural" price indicates that the commodity will likely experience windfall profits or losses. When the supply and the "effective demand" are in sync, the "market" price would end up corresponding to the "natural" price. The profit rate earned in that sector is the same as the profit rate earned across the whole economy, and it is stated that the conditions of equilibrium will prevail. Therefore, according to this specific approach, supply and demand changes only explain are indicative of the deviation that occur of "market" from "natural" prices. The "long period technique" was once again implemented by the economists who later on developed the neoclassical theory. Unlike the classical political economics theory, the neoclassical economics theory set distribution, pricing, and output all at the same time. All of these variables' "natural" or "equilibrium" values relied heavily on technological conditions of production and were consequently linked to the "attainment of a uniform rate of profits in the economy."

The transition from the short run to the long run may be done by considering some short run equilibrium that is also a long run equilibrium as to supply and demand, then comparing that state against a new short run and long run equilibrium state from a change that disturbs equilibrium, say in the sales tax rate, tracing out the short run adjustment first, then the long run adjustment. Each is an example of comparative statics. Alfred Marshall (1890) pioneered in comparative static period analysis. He distinguished between the temporary or market period (with output fixed), the short period, and the long period. "Classic" contemporary graphical and formal treatments include those of Jacob Viner (1931), John Hicks (1939), and Paul Samuelson (1947). The law is related to a positive slope of the short run marginal cost curve.

The usage of long run and short run in macroeconomics differs somewhat from the above microeconomic usage. John Maynard Keynes in 1936 emphasized fundamental factors of a market economy that might result in prolonged periods away from full employment. In later macroeconomic usage, the long run is the period in which the price level for the overall economy is completely flexible as to shifts in aggregate demand and aggregate supply. In addition there is full mobility of labor and capital between sectors of the economy and full capital mobility between nations. In the short run none of these conditions need fully hold. The price level is sticky or fixed in response to changes in aggregate demand or supply, capital is not fully mobile between sectors, and capital is not fully mobile across countries due to interest rate differences among countries and fixed exchange rates. A famous critique of neglecting short run analysis was by Keynes, who wrote that "In the long run, we are all dead", referring to the long run proposition of the quantity theory of money, for example, a doubling of the money supply doubling the price level.

The short period equilibria' has been sometimes applied to post Walrasian equilibria. On other occasions, Keynes's notion of equilibrium was mostly treated as temporary equilibrium. There were great differences between the post Walrath model, Marshall model, and Keynes model. The post Walrath model gives all capital goods, including mobile capital goods; Whereas in Marshall's short term analysis, only the fixed factories of a single industry are a figure, in Keynes's work, only the fixed capital goods of the entire economy are given. The term ' long period equilibrium' was often used to refer to post Walrasian intertemporal equilibria with futures markets, sequences of temporary equilibria, and steady growth equilibria. All these show huge ambiguity in the notion of equilibrium.