The NBER's Business Cycle Dating Committee maintains a chronology of the U. A recession is a period between a peak and a trough, and an expansion is a period between a trough and a peak.
The chronology comprises alternating dates of peaks and troughs in economic activity.
During a recession, a significant decline in economic activity spreads across the economy and can last from a few months to more than a year.
In both recessions and expansions, brief reversals in economic activity may occur-a recession may include a short period of expansion followed by further decline; an expansion may include a short period of contraction followed by further growth.
The Committee applies its judgment based on the above definitions of recessions and expansions and has no fixed rule to determine whether a contraction is only a short interruption of an expansion, or an expansion is only a short interruption of a contraction.
The most recent example of such a judgment that was less than obvious was in 1980-1982, when the Committee determined that the contraction that began in 1981 was not a continuation of the one that began in 1980, but rather a separate full recession.
The Committee does not have a fixed definition of economic activity.
It examines and compares the behavior of various measures of broad activity: real GDP measured on the product and income sides, economy-wide employment, and real income.