Prior to 1979, there were no formal announcements of business cycle turning points.
The NBER does not define a recession in terms of two consecutive quarters of decline in real GDP. Rather, a recession is a significant decline in economic activity spread across the economy, lasting more than a few months, normally visible in real GDP, real income, employment, industrial production, and wholesale-retail sales. For more information, see the latest announcement from the NBER's Business Cycle Dating Committee, dated 9/20/10.
The explanation of fluctuations in aggregate economic activity is one of the primary concerns of macroeconomics . The main framework for explaining such fluctuations is Keynesian economics . In the Keynesian view, business cycles reflect the possibility that the economy may reach short-run equilibrium at levels below or above full employment . If the economy is operating with less than full employment, ., with high unemployment , Keynesian theory states that monetary policy and fiscal policy can have a positive role to play in smoothing the fluctuations of the business cycle.