On September 20, the NBER’s Business Cycle Dating Committee announced that the end of the Great Recession occurred in June 2009 (announcement here). This lag of about three months is reasonably fast as NBER announcements go – the goal is to be right not fast. The Great Recession began in December 2007 and so lasted 18 months, making it the longest in the post-war period. Why does the NBER get to date business cycles? Because they did it first. Burns, Mitchell, and Kuznets developed the methods to measure macroeconomic performance, measured macroeconomic performance, and defined business cycles. How does the NBER dates cycles? Read FAQs here and the procedure here. A complete list of cycles is here. Of note, the Great Depression was really two recession and a lot of sluggish growth.