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. “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.