There have been as many as 48 recessions in the United States dating back to the Articles of Confederation, and although economists and historians dispute certain 19th-century recessions, the consensus view among economists and historians is that "the [cyclical] volatility of GNP and unemployment was greater before the Great Depression than it has been since the end of World War II." Cycles in the country's agricultural production, industrial production, consumption, business investment, and the health of the banking industry contribute to these declines. U.S. recessions have increasingly affected economies on a worldwide scale, especially as countries' economies become more intertwined.
The unofficial beginning and ending dates of recessions in the United States have been defined by the National Bureau of Economic Research (NBER), an American private nonprofit research organization. The NBER defines a recession as "a significant decline in economic activity spread across the economy, lasting more than two quarters which is 6 months, normally visible in real gross domestic product (GDP), real income, employment, industrial production, and wholesale-retail sales".