Now that progress could be in jeopardy. Evidence is growing that trade tensions and slowing global growth are taking a toll on the American economy; this week, data showed that the manufacturing sector was contracting. The job market has escaped significant damage so far, but it is unclear how long that can last.

Dell’s executives say that their recruitment efforts are part of a long-term strategy to diversify its work force, and that the company won’t abandon them just because the unemployment rate ticks back up.

Economists, however, said they doubt most companies will keep such programs in place when the next recession hits. Similar policies adopted during the late 1990s and early 2000s largely disappeared after the dot-com bubble burst, and didn’t make a comeback even during the relatively healthy job market later that decade.

That, many economists say, is why it is so important to keep the current expansion — already the longest on record — going for as long as possible.

“I think all these gains are incredibly fragile, and they need to be fostered and protected,” said Julia Pollak , a labor economist for the employment site ZipRecruiter.

Even now, there is evidence that the job market has room for further improvement. Companies are raising pay, but only gradually, and the inflow of workers into the labor force has slowed in recent months.

For workers hired during the good times, the benefits can be enduring. Economic research has found that once people are drawn into the labor force, they tend to stay in it. That may be especially true for workers with disabilities or other barriers to employment who thrive once given a job — but who struggle to get that chance in all but the strongest job markets.