According to the National Bureau of Economic Research (NBER), the U.S. economy was in a recession for 18 months from December 2007 to June 2009. It was the longest and deepest recession of the post-World War II era. This report provides information on the patterns found across past recessions since World War II to gauge whether and how this recession might be different. There is no simple, rule-of-thumb measure to determine when recessions begin or end. Recessions are officially declared by the National Bureau of Economic Research (NBER), a non-profit research organization. The NBER defines a recession as a "significant decline in economic activity spread across the economy, lasting more than a few months" based on a number of economic indicators, with an emphasis on trends in employment and income. It is unlikely that all of those indicators will begin declining or rising simultaneously. Thus, when comparing historical episodes, some of the symptoms associated with a recession may occur before or after the recession has officially begun or ended. In the recent episode, gross domestic product (GDP) began to fall (in the fourth quarter of 2007) before employment (in January 2008), and both deteriorated significantly in the third quarter of 2008. The economy began to grow again in the third quarter of 2009, but employment continued to fall through December 2009. Recessions are not uncommon—2008 marked the 11 t h since World War II. In recent years, recessions have been less frequent—from 1982 to 2001, there were only two recessions—but the length between the recent one and the prior one, 73 months, was comparable to the frequency of recessions from 1945 to 1981. As can be seen from Table 1 , the recent recession was 18 months long, making it the longest of the post-war period. It was almost twice as long as the median length of post-war recessions (9.5 months). Recessions end because of monetary and fiscal stimulus—both were employed in the recent episode —and because markets automatically adjust. Recessions affect economic well-being by their length and depth. When considering depth, the recent recession can be separated into two distinct phases. During the first phase, which lasted for the first two quarters of 2008, the recession was not deep as measured by the change in GDP or unemployment. It deepened in the third quarter of 2008, however, and remained deep through the first quarter of 2009. After a slight further decline in the second quarter, the economy returned to expansion in the third quarter of 2009. The fall in GDP during the recent recession, a cumulative 4.1%, was the deepest of the post-war period. By contrast, output fell by 1.4% in the 1990-1991 recession and 0.3% in the 2001 recession. The decline in output after the second quarter of 2008 was even larger than over the entire recession. Most of the decline occurred from the third quarter of 2008 to the first quarter of 2009. The 1981 recession was the last recession to feature consecutive quarters of steep declines in GDP. The 1973 and 1981 recessions were also unusually long and deep, in terms of lost output. During the recession beginning in 1973, GDP fell by a cumulative 3%. During the recession beginning in 1981, GDP fell by a cumulative 2.9%, and this recession came on the heels of a 2.2% decline in GDP in a separate recession one year earlier. Economists often attribute the unusual length and depth of the 1973 and 1981 recessions in part to the Federal Reserve's decision to keep interest rates high. The rate targeted by the Fed, the federal funds rate, peaked at 12.9% in July 1974 and 19% in July 1981. (After adjusting for inflation, these rates were not nearly as high as they appear because inflation was so much higher at the time.) The Fed had raised rates that high in order to reduce inflation, which, as measured in the GDP accounts, peaked at an annualized rate of 12.8% in the third quarter of 1974 and 11.1% in the fourth quarter of 1980. For that reason, some economists have described these recessions as "made in Washington"—had the Fed not raised rates so high, they argue, the recessions would presumably have been shorter and milder (although inflationary problems might have worsened). This dynamic has not been important in the recent recession, as the federal funds rate's recent peak was 5.25% and was reduced before the recession had begun, eventually falling to almost zero. Rising inflation was initially a concern in the current episode, but has never come close to the rates of the 1970s and 1980s—it peaked at 4.2% in the first quarter of 2007. Rising energy and commodity prices were temporarily pushing inflation up in the first half of 2008. Since then, declines in those prices temporarily led to deflation (falling prices) at the end of 2008, with very low inflation since. As the economy gradually recovers, views are divided on the outlook for inflation. Some commentators point to a federal funds rate of zero and the unprecedented scale of the Fed's intervention in financial markets as policies that will ultimately push inflation higher. Through direct lending and asset purchases, the Fed's outstanding support to the financial sector has, at times, exceeded $1 trillion, compared with less than $1 billion before the financial crisis began. In normal times, such interest rate and lending policies would be expected to be highly inflationary. But as the recession drove down aggregate demand, it put downward pressure on inflation. Other commentators fear that the recession was severe enough that deflation is a greater threat than inflation. They argue that the Fed's intervention in financial markets was necessary to avoid a "liquidity trap," where lower interest rates no longer stimulate interest-sensitive spending. Although the Fed has brought the federal funds rate down to near zero, because it was only 5.25% when the Fed began reducing rates, the Fed's scope for easing monetary policy through traditional methods was somewhat limited. By contrast, the federal funds rate, although high, was reduced (peak to trough) by 6.8 percentage points in the 1973 recession and by 10.5 percentage points in the 1981 recession. Table 2 shows the rise in unemployment in all 11 post-war recessions. Unsurprisingly, the recessions with the deepest declines in output also featured the largest increases in unemployment. From the expansion peak to post-recession high, the 1973 recession saw an increase in the unemployment rate of 4.2 percentage points, and the 1981 recession saw an increase of 3.6 percentage points (or 4.8 percentage points compared with the expansion that ended in 1980). Unemployment peaked at 10.1% in October 2009, a 5.1 percentage point increase compared with the previous expansion peak. The 1981-1982 recession was the only other recession in the post-war period in which unemployment topped 10%. Most of the increase in unemployment in the recent recession occurred after the first six months of the recession, underlining the initial mildness of the recession. The rise in the unemployment rate during this recession was comparable to the recessions since 1960 for the first 10 months following the recession's onset. Beginning in the 11 th month, however, it followed a pattern similar but even more severe than the two "deep and long" recessions of 1973 and 1980. (Unemployment leveled off after about a year in the other four recessions since 1960.) The recent recession eventually featured the largest increase in unemployment in the post-war period. Unemployment rose for 22 months, the longest period of rising unemployment since World War II. The 1973 and 1981 recessions were the only other two in the post-war period where unemployment continued to rise after about a year; in the 1973 recession, it rose for 19 months. The previous two recessions, in 1991 and 2001, were mild and brief as measured by the decline in GDP, and had some of the smallest increases in unemployment in the post-war period. This is not the whole story, however, because, in both cases, unemployment continued to rise for over a year after the recession had ended. (In every other post-war recession, with the exception of the one beginning in November 1970, unemployment began falling within six months of the recession's end.) These two episodes have therefore been called "jobless recoveries." If the rise in unemployment in the jobless recovery were included, the episode beginning in 1991 would have featured an above average rise in unemployment; but the episode beginning in 2001 would still remain below average. It is unclear whether the economy has changed in some fundamental way that makes jobless recoveries more likely from now on, or if it was simply a coincidence that the previous two recessions ended in this way. Job growth following the recent recession was more typical in that employment began rising in January 2010, seven months after the recession officially ended. Less typically, subsequent employment growth has been weak. The recent recession has also featured the largest decrease in consumption and private fixed investment spending of any post-war recession. There are a few commonalities found across all previous post-war recessions. First, in all cases, consumption spending did not weaken as much as GDP, as shown in Table 1 . In fact, in five out of 11 recessions, consumption continued to grow while GDP fell. To the extent that households can adjust their saving and borrowing levels, they are thought to generally prefer to "smooth" consumption over time, avoiding sudden increases and decreases. In the recent recession, consumption declined relatively rapidly in the third and fourth quarters of 2008, with small positive and negative changes in the other quarters. Consistent with the historical pattern, consumption has fallen by proportionately less than output cumulatively. Second, in all recessions, fixed investment spending fell more sharply than GDP. This evidence casts doubt on a popular explanation that recessions are caused by declines in consumption. It suggests to some that the primary driver of the business cycle is cyclical changes in investment demand.