NBER and Recessions

Many people think the definition of a recession is two consecutive quarters of decline in the gross domestic product. But that's a misperception. Hall and his colleagues will look beyond such simple metrics, weighing monthly GDP estimates, employment data, income, industrial production, and other factors. To call a recession, they'll look for clear signs of "a significant decline in economic activity spread across the economy, lasting more than a few months."

Any call, if it comes, is going to take a while. The NBER usually takes 6 to 18 months to decide when a recession starts or ends. Hall's committee didn't announce the end of the 2001 recession until a full 20 months after the fact.

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