NBER ; United States Recession Criteria

In the US, the judgment of the business-cycle dating committee of the National Bureau of Economic Research regarding the exact dating of recessions is generally accepted. The NBER has a more general framework for judging recessions:

The 2001 recession was announced by the NBER in November 2001[9], which later turned out to be the truth. Thus the recession ended the month it was announced by the NBER. In July 1981 the NBER declared an end to a six-month recession from January to July 1980, the last year of Jimmy Carter's presidency. For the 1981-82 recession, which was during President Reagan's first term, the NBER announced the July 1981 peak in January 1983, and the November 1982 trough in July 1983.[10]

Economist Robert J. Gordon, a member of the NBER committee has stated that any announcement about the start of a new recession starting in 2008 is unlikely before the last few months of 2008 at the earliest[11].

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. A recession begins just after the economy reaches a peak of activity and ends as the economy reaches its trough.

Because of the way a recession is defined, the beginning (peak in the economic cycle) or end (trough) of a recession can only be identified after the change in the trend has been present for several months.