According to an analysis by Steve Goss, chief actuary for the Social Security Administration, about 200,000 more people filed initial claims in 2009 and 2010 than the agency had predicted before the recession and he said the trend most likely continued in 2011 and 2012, though that is harder to quantify. The most likely reason is joblessness.

Ms. Keany had always expected to work into her 70s and add to her retirement cushion. But after losing her job as an executive assistant at an advertising agency in 2008, she searched fruitlessly for full-time work and exhausted her unemployment benefits. For a while, she strung together odd jobs and lived off her 401(k) retirement and profit-sharing accounts. Then, this year, with her savings depleted and no job offers in sight, she reluctantly applied for Social Security.

Gazing out the window where the Santa Rosa mountains rise behind the mobile home park, she said, “It just seems a waste of a life, to be honest.”

Drawing Social Security early has repercussions that will be hard to overcome even if the economy — and her work prospects — improve. By collecting four years shy of her full retirement age, Ms. Keany will receive a reduced monthly benefit for the rest of her life. Those who collect early get 20 to 30 percent less a month than they would get if they waited until full retirement age, which varies by year of birth. People in Ms. Keany’s age bracket are expected to live an average of close to 23 more years.

“The most potent lever that individuals can pull in trying to get themselves a secure retirement income is to postpone claiming” Social Security, said Alicia H. Munnell, director of the Center for Retirement Research at Boston College.