Even if claimants have more ambiguous medical cases, once they are granted disability benefits, they generally continue to collect. Of the 567,395 medical reviews conducted on beneficiaries in 2009, Social Security expects less than 1 percent to leave because of improved health.

The benefits have no expiration date, like the current 99-week limit for collecting unemployment. And because many people spend years appealing denials and building their medical case before being granted benefits, their skills often atrophy and gaps open on their résumés, making it more difficult for them to get back to work.

Beneficiaries, who also fear losing health care coverage, may view their checks as birds in the hand. “Even if you’re taking just $800 or $900 a month, that’s better than nothing,” said Bruce Growick, an associate professor of rehabilitation services at Ohio State University.

Shortly after Mr. Howard’s benefit checks started arriving, he received a four-by-six-inch card from Social Security informing him of services to help him return to work. Confused by the bureaucratic language and fearing the loss of medical coverage, he discarded it. When he called the local office, he said a staff member did not seem to know what his rights were or what help was available.

“I thought it is just better to get what we are getting,” he said.

In fact, Social Security offers disability beneficiaries some incentive to ease back into the work force. For nine months after starting a job, they can earn any amount without threatening their benefits. For another three years, if their income falls below $1,000 a month, they can immediately receive full benefits again. And they can keep Medicare coverage for eight and a half years after going back to work, something few beneficiaries may realize.

In 1999, Congress passed a law authorizing the Ticket to Work program, which offers beneficiaries practical help with a job search. Social Security also waives medical reviews for those who participate.

So far, the program has had little success. Out of 12.5 million disabled workers and those who receive benefits for the disabled poor, only 13,656 returned to work over the last two and a half years, with less than a third of them earning enough to drop the benefits.