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In economics, deflation is a decrease in the general price level of goods and services.〔Robert J. Barro and Vittorio Grilli (1994), ''European Macroeconomics'', chap. 8, p. 142. ISBN 0-333-57764-7〕 Deflation occurs when the inflation rate falls below 0% (a negative inflation rate). This should not be confused with disinflation, a slow-down in the inflation rate (i.e., when inflation declines to lower levels). Inflation reduces the real value of money over time; conversely, deflation increases the real value of money — the currency of a national or regional economy. This allows one to buy more goods with the same amount of money over time. Economists generally believe that deflation is a problem in a modern economy because it increases the real value of debt, and may aggravate recessions and lead to a deflationary spiral.〔Hummel, Jeffrey Rogers. "Death and Taxes, Including Inflation: the Public versus Economists" (Jan 2007). ()〕 Although the values of capital assets are often casually said to "deflate" when they decline, this should not be confused with deflation as a defined term; a more accurate description for a decrease in the value of a capital asset is economic depreciation (which should not be confused with the accounting convention of depreciation, which are standards to determine a decrease in values of capital assets when market values are not readily available or practical). ==Causes and corresponding types== In the IS/LM model (Investment and Saving equilibrium/ Liquidity Preference and Money Supply equilibrium model), deflation is caused by a shift in the supply and demand curve for goods and services, particularly a fall in the aggregate level of demand. That is, there is a fall in how much the whole economy is willing to buy, and the going price for goods. Because the price of goods is falling, consumers have an incentive to delay purchases and consumption until prices fall further, which in turn reduces overall economic activity. Since this idles the productive capacity, investment also falls, leading to further reductions in aggregate demand. This is the deflationary spiral. An answer to falling aggregate demand is stimulus, either from the central bank, by expanding the money supply, or by the fiscal authority to increase demand, and to borrow at interest rates which are below those available to private entities. In more recent economic thinking, deflation is related to risk: where the risk-adjusted return on assets drops to negative, investors and buyers will hoard currency rather than invest it, even in the most solid of securities. This can produce a liquidity trap or it may lead to shortages that entice investments yielding more jobs and commodity production. A central bank cannot, normally, charge negative interest for money, and even charging zero interest often produces less stimulative effect than slightly higher rates of interest. In a closed economy, this is because charging zero interest also means having zero return on government securities, or even negative return on short maturities. In an open economy it creates a carry trade, and devalues the currency. A devalued currency produces higher prices for imports without necessarily stimulating exports to a like degree. In monetarist theory, deflation must be associated with either a reduction in the money supply, a reduction in the velocity of money or an increase in the number of transactions. But any of these may occur separately without deflation. It may be attributed to a dramatic contraction of the money supply, or to adherence to a gold standard or other external monetary base requirement. However, deflation is the natural condition of hard currency economies when the supply of money does not grow as quickly as population and the economy. When this happens, the available amount of hard currency per person falls, in effect making money more scarce, and consequently, the purchasing power of each unit of currency increases. Deflation occurs when improvements in production efficiency lower the overall price of goods. Competition in the marketplace often prompts those producers to apply at least some portion of these cost savings into reducing the asking price for their goods. When this happens, consumers pay less for those goods, and consequently deflation has occurred, since purchasing power has increased. Rising productivity and reduced transportation cost created structural deflation during the acceleration productivity era of from 1870–1900,〔 but there was mild inflation for about a decade before the establishment of the Federal Reserve in 1913. There was inflation during World War I, but deflation returned again after that war and during the 1930s depression. Most nations abandoned the gold standard in the 1930s. There is less reason to expect deflation, aside from the collapse of speculative asset classes, under a fiat monetary system with low productivity growth. In mainstream economics, deflation may be caused by a combination of the supply and demand for goods and the supply and demand for money, specifically the supply of money going down and the supply of goods going up. Historic episodes of deflation have often been associated with the supply of goods going up (due to increased productivity) without an increase in the supply of money, or (as with the Great Depression and possibly Japan in the early 1990s) the demand for goods going down combined with a decrease in the money supply. Studies of the Great Depression by Ben Bernanke have indicated that, in response to decreased demand, the Federal Reserve of the time decreased the money supply, hence contributing to deflation. Demand-side causes are: * Growth deflation: an enduring decrease in the real cost of goods and services as the result of technological progress, accompanied by competitive price cuts, resulting in an increase in aggregate demand. :A structural deflation existed from the 1870s until the cycle upswing that started in 1895. The deflation was caused by the decrease in the production and distribution costs of goods. It resulted in competitive price cuts when markets were oversupplied. The mild inflation after 1895 was attributed to the increase in gold supply that had been occurring for decades.〔 〕 There was a sharp rise in prices during World War I, but deflation returned at the war's end. By contrast, under a fiat monetary system, there was high productivity growth from the end of World War II until the 1960s, but no deflation. :Historically not all episodes of deflation correspond with periods of poor economic growth.〔Andrew Atkeson and Patrick J. Kehoe of the Federal Reserve Bank of Minneapolis (Deflation and Depression: Is There an Empirical Link? )〕 :See: Deflation#Scarcity of official money. :Productivity and deflation are discussed in a 1940 study by the Brookings Institution that gives productivity by major US industries from 1919 to 1939, along with real and nominal wages. Persistent deflation was clearly understood as being the result of the enormous gains in productivity of the period. By the late 1920s, most goods were over supplied, which contributed to high unemployment during the Great Depression. * Cash building (hoarding) deflation: attempts to save more cash by a reduction in consumption leading to a decrease in velocity of money. Supply-side causes are: * Bank credit deflation: a decrease in the bank credit supply due to bank failures or increased perceived risk of defaults by private entities or a contraction of the money supply by the central bank. 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「deflation」の詳細全文を読む スポンサード リンク
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