A History Of American Recessions | ZeroHedge

The official designation of a recession comes from a committee at the National Bureau of Economic Research (NBER), a private, nonprofit research organization. - Tyler Durden
The committee considers a wide range of economy-wide, monthly data points, but the NBER views GDP as “the single best measure.”
The committee calls a recession once there is a significant decline across these measures for more than a few months.
Using this measure, here's a few insights:

• From 1855 to 2020, recessions lasted an average of 17 months. 
• In the 20th and 21st centuries, the average recession has decreased to 14 months....