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In economics, Okun's law (named after Arthur Melvin Okun, who proposed the relationship in 1962〔Prachowny, 1993.〕) is an empirically observed relationship between unemployment and losses in a country's production. The "gap version" states that for every 1% increase in the unemployment rate, a country's GDP will be roughly an additional 2% lower than its potential GDP. The "difference version" 〔Knotek, 75〕 describes the relationship between quarterly changes in unemployment and quarterly changes in real GDP. The stability and usefulness of the law has been disputed.〔Knotek, 93〕 ==Imperfect relationship== Okun's law is more accurately called "Okun's rule of thumb" because it is primarily an empirical observation rather than a result derived from theory. Okun's law is approximate because factors other than employment (such as productivity) affect output. In Okun's original statement of his law, 2% increase in output corresponds to a 1% decline in the rate of cyclical unemployment; a .5% increase in labor force participation; a .5% increase in hours worked per employee; and a 1% increase in output per hours worked (labor productivity).〔Okun, 1962〕 Okun's law states that a one point increase in the cyclical unemployment rate is associated with two percentage points of negative growth in real GDP. The relationship varies depending on the country and time period under consideration. The relationship has been tested by regressing GDP or GNP growth on change in the unemployment rate. Martin Prachowny estimated about a 3% decrease in output for every 1% increase in the unemployment rate. However, he argued that the majority of this change in output is actually due to changes in factors other than unemployment, such as capacity utilization and hours worked. Holding these other factors constant reduces the association between unemployment and GDP to around 0.7% for every 1% change in the unemployment rate (Prachowny 1993). The magnitude of the decrease seems to be declining over time in the United States. According to Andrew Abel and Ben Bernanke, estimates based on data from more recent years give about a 2% decrease in output for every 1% increase in unemployment (Abel and Bernanke, 2005). There are several reasons why GDP may increase or decrease more rapidly than unemployment decreases or increases: As unemployment increases, * a reduction in the multiplier effect created by the circulation of money from employees * unemployed persons may drop out of the labor force (stop seeking work), after which they are no longer counted in unemployment statistics * employed workers may work shorter hours * labor productivity may decrease, perhaps because employers retain more workers than they need One implication of Okun's law is that an increase in labor productivity or an increase in the size of the labor force can mean that real net output grows without net unemployment rates falling (the phenomenon of "jobless growth") 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「Okun's law」の詳細全文を読む スポンサード リンク
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