Soon after we first talked in October, Ms. Barrington-Ward left her sister’s house in Ohio, where she had crashed for six weeks, and went back to Boston and filed her bankruptcy paperwork. She contacted a headhunter. “I’ve got to get a job,” she said. “I just have to.” She had two job interviews lined up and her fingers crossed.

Long-term joblessness — the kind that Ms. Barrington-Ward and about four million others are experiencing — is now one of the defining realities of the American work force.

The unemployment rate has fallen to 7.3 percent, down from 10 percent four years ago. Private businesses have added about 7.6 million positions over the same period. But while recent numbers show that there are about as many people unemployed for short periods as in 2007 — before the crisis hit — they also show that long-term joblessness is up 213 percent.

In part, that’s because people don’t return to work in an orderly, first-fired, first-hired fashion. In any given month, a newly jobless worker has about a 20 to 30 percent chance of finding a new job. By the time he or she has been out of work for six months, though, the chance drops to one in 10, according to research by the Federal Reserve Bank of San Francisco.

Facing those kinds of odds, some of the long-term jobless have simply given up and dropped out of the labor force. So while official figures show that the number of long-term jobless has fallen steeply from its recessionary high of 6.7 million, many researchers fear that this number could mean as much bad news as good. Workers over 50 may be biding their time until they can start receiving Social Security. Younger workers may be going to school to avoid a tough job market. Others may be going on disability, helping to explain that program’s surging rolls.

Stan Hampton, 59, a veteran of the Iraq war, is now earning his associate degree. But he has not had a job since returning from active duty in 2007, and is now living in an apartment complex for veterans near Las Vegas.