Business cycles are intervals of general expansion followed by recession in economic performance. The changes in economic activity that characterize business cycles have important implications for the welfare of the general population, government institutions, and private sector firms.
There are many definitions of a business cycle. The simplest defines recessions as two consecutive quarters of negative GDP growth. More satisfactory classifications are provided first by including more economic indicators and second by looking for more data patterns than the two quarter definition. In the United States, the National Bureau of Economic Research oversees a Business Cycle Dating Committee that defines a recession as "a significant decline in economic activity spread across the market, lasting more than a few months, normally visible in real GDP, real income, employment, industrial production, and wholesale-retail sales."