The MIT Dictionary of Modern Economics defines deflation as "A sustained fall in the general price level."1 Deflation represents the opposite of inflation, which is defined as an increase in the overall price level over a period of time. In contrast, disinflation, represents a period when the inflation rate is positive, but declining over time.
Deflation, inflation, and disinflation represent different behavior of the price level. The price level is commonly measured using either a Gross Domestic Product Deflator (GDP Deflator) or a Consumer Price Index (CPI) indicator. The GDP Deflator is a broad index of inflation in the economy; the CPI Index measures changes in the price level of a broad basket of consumer products. The Chart shows the monthly percentage change in the CPI (all urban consumers, all items) over the prior 12-month period, and includes periods of deflation, inflation, and disinflation in consumer prices.
Two brief periods, the first from approximately mid-1949 to mid-1950, and the second, approximately from the fall of 1954 to the summer of 1955, shown in Chart, indicate brief periods of deflation in the consumer price index. Other than these two brief periods, the CPI Index shows inflation in consumer prices over nearly the entire 1947 to 1999 period. The period from mid-1980 to mid-1983 indicates a period of disinflation, a period when the rate of inflation was declining from month to month.
Periods of deflation typically are associated with downturns in the economy. The two temporary periods of deflation corresponded to recessions in the U.S. economy. However, periods of deflation need not be as short as these two brief episodes in the 1950s. During the Great Depression of the 1930s the nation experienced a long period of deflation. As noted by Samuelson and Nordhaus (1998), "Sustained deflations, in which prices fall steadily over a period of several years, are associated with depressions, such as occurred in the 1930s or the 1890s."2
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