Back when the stock market seemed to go in only one direction—up— you could make a decent case for keeping a mortgage as long as possible. Why rush to pay off a debt at, say, 6 percent, when the same money, invested in the stock market, was all but guaranteed to return 10 percent?

That kind of thinking may help explain this startling finding in a just-released Society of Actuaries report: Only 48 percent of retirees surveyed in 2009 had completely paid off their mortgages, compared with 76 percent in the group’s 2007 study.

Other forces probably came into play, too, including the refinancing boom, and, more recently, people forced to retire early because of the recession. 

Whatever the reasons, it seems that the majority of retirees are now writing mortgage checks. Should you plan to join them when your day comes?