The jobs crisis has brought a sad discovery for many unemployed Americans: Openings in their old fields exist; yet they no longer qualify.

This trend took root in the recession. Companies had to do more with fewer workers. Some asked staffers to take on broader duties once spread among several jobs.

Some database administrators must now manage network security. Accountants must do financial analysis to find ways to cut costs. Factory workers must program computers to run machinery.

So it's hard to fill many jobs that are open these days. Many companies say they can't find qualified people for certain jobs, even with 4.6 unemployed Americans, on average, vying for each opening.

The total number of job openings is historically low: 3.2 million, down from 4.4 million before the recession. But as the number of openings has surged 37 percent in the past year, the unemployment rate has risen.

When Bayer Material-Science, a unit of Bayer, sought a new health, safety and environment director for a plant, it wanted a wider range of skills than before: someone skilled not just in managing health and safety but also in guiding employees to adapt to workplace changes.

The company interviewed 30 candidates, then did final interviews with seven. But none had the additional experience the company now wanted. The company finally chose one of its own workers.

David Altig, research director at the Federal Reserve Bank of Atlanta, says workers are being asked not just to increase their output but to broaden it. A company might have had three back-office jobs before the recession, Altig said, only one of which required computer skills. Now, he said, "one person is doing all three of those jobs - and every job you fill has to have computer skills."

The trend magnifies the obstacles facing the unemployed. Economists have long worried that millions of people who have lost jobs in depressed fields such as construction don't qualify for work in growing sectors such as health care. But some of the jobless no longer even qualify for their old positions.

Frustrated in searching for qualified applicants among the jobless, employers are turning to those already employed.

Only 49 percent of people laid off from 2007 through 2009 were re-employed by January 2010, a Labor Department survey says. It's the lowest figure since the survey began in 1984.