Are we due for a recession? It has been 66 months since the last recession ended (as I write this in December 2014). Not too many people felt that the recession was over back in June 2009, but that's what the business cycle experts determined. Does the length of this expansion tell us that we're due for another one soon?

In economists' jargon, a business cycle consists of an expansion, when the GDP and other measures are increasing, and a recession, when GDP is declining. To avoid calling every temporary drop a recession, we look for sustained and widespread declines in economic activity before using the label recession.

Plenty of damage has been done by our phrase “business cycle.” The first thing to understand is that business fluctuations look nothing like a regular cycle. Consider our experience in the post-World War II era:

Thus, there's nothing regular about these cycles. (This article focuses on the United States experience, but other countries are roughly comparable regarding the main points.)

In nearly 70 years the since the end of World War II, we have had 11 recessions, or about one every six years on average.

Expansions don't die of old age; they are murdered. That is, recessions don't occur just because there has been a lengthy expansion. The probability of going into a recession is no higher when the expansion is old than when it's young. Recessions are the result of errors. The government, especially the Federal Reserve, is responsible for many of the errors that cause recessions, but private sector errors also play a role.

Prior to World War II, recessions were more frequent. In the hundred years prior to the war, we had 22 recessions, for one every 4.5 years on average. The recessions were, on average, longer in the earlier period, while the expansions were shorter.