The United States-based National Bureau of Economic Research (NBER*) defines economic recession as: "a significant decline in [the] economic activity spread across the country, lasting more than a few months, normally visible in real GDP growth, real personal income, employment (non-farm payrolls), industrial production, and wholesale-retail sales.

*The NBER's Business Cycle Dating Committee is generally seen as the authority for dating US recessions. Academic economists, policy makers, and businesses all usually refer to recessions as determined by the NBER. ( Edited by plmiller )  

http://www.bargaineering.com/articles/what-to-d...