(Bloomberg) — Mortgage-burning parties in the U.S. may be going the way of home milk deliveries and polyester leisure suits.

A growing number of homeowners are reaching retirement age still owing money on their houses. The share of Americans 65 and older with mortgage debt rose to 30 percent in 2011 from 22 percent in 2001, according to a May analysis by the Consumer Financial Protection Bureau based on the latest available figures. Loan balances also increased, with the median amount owed climbing to $79,000 from $43,400 after adjusting for inflation, the data showed.

"There were old-fashioned beliefs probably 30 years ago" that included "you should pay off your house before you retire," said Olivia Mitchell, executive director of the Pension Research Council at the University of Pennsylvania's Wharton School in Philadelphia. "This is no longer the case."