Actually, NBER doesn’t officially use the word “recession” as such, but dates the turning points of business cycles, Malpezzi says. Once they date a “peak,” we’re in a downturn, or a contraction, and once they date a “trough” we’re in a recovery, or an expansion.

Since 1900, we’ve had 22 peaks and therefore 22 contractions. In common parlance, two of those contractions (and an intervening expansion!) ran from August 1929 to June 1938, and it’s this period that we refer to as the “Great Depression.” We call the other contractions “recessions.”

Gross domestic product (GDP) is the benchmark measure of our economy’s output. “It’s commonly said that a recession is a period of two consecutive quarters of decline in GDP,” Malpezzi says. “But actually, NBER looks at a range of economic indicators, including trade, industrial output and so on, but paying particular attention to GDP and employment.”

In fact, back in December 11, 2008, NBER officially “called” a peak, and therefore a recession, in December 2007. GDP data had not yet shown declines, but its growth was weak, and employment had reached a peak.

There is no official arbiter, or definition, of “depression,” Malpezzi says. But simply put, a depression is a really deep and long recession. The 1929 to 1938 Great Depression saw a decline in real GDP of roughly 30 percent from peak to trough, and an unemployment rate of around 25 percent, much greater than any loss since that time. While economists still debate the causes of the Depression, there is a consensus that its length was related to policy failures by the government and especially the Federal Reserve.