The Princeton economist Alan Krueger started with a question: What’s keeping young people out of work?  

Over the last two decades, the share of employed Americans in their prime has steadily tumbled — even as the economy recovered and businesses nationwide struggled to fill openings.

In a new paper, Krueger argues that opioids pose more than just a health threat: They’re benching workers across the country.

“The problem of the depressed labor force has run into the problem of the opioid crisis,” he said. “Now they’re connected.”

The rise in painkiller prescriptions between 1999 and 2015 drove about 20 percent of the drop in men’s workforce participation and 25 percent of women’s, Krueger estimated in the study, out Thursday.

To reach this conclusion, the economist looked at county-level opioid prescription rates and labor force data from the periods of 1999 to 2001 and 2014 to 2016.

Areas with the highest rates of opioid prescriptions, Krueger noticed, also experienced a shrinking workforce. The dark green splotches in this Brookings Institution map show that swaths of Nevada, Michigan, Maine, the southeast and the southwest appear to have suffered the hardest hits.

He also found that unemployed men and women both reported higher use of painkillers than their counterparts with jobs.

In surveys, Krueger saw that 44 percent of out-of-work men said they’d taken pain medication within the last 24 hours, though that could include something as innocuous as ibuprofen. Still, their rate was more than double that of the working men.

Among prime age women, though, the gap was less dramatic. Some 34.7 percent of women who’d dropped out of the labor force said they were taking painkillers, compared to 25.7 percent for those with jobs.

“Women take opioids, just like men,” Krueger said. “The magnitudes are pretty similar.”

Reliance on the addictive medication could have rendered more adults unable to work, Krueger said. A national survey of employers this year revealed that failed drug tests just soared to a 12-year high.

Krueger added that he wants lawmakers to do more than declare the opioid crisis a “national emergency,” as President Trump has done. Policymakers, he said, should focus on guiding people toward work and away from developing a drug habit.

“At a personal level, I think people are not very satisfied with their lives when they’re out of the labor force,” he said, “and from an economic standpoint, they’re on the sidelines. They’re not even on the team.”

Today, 12 percent of “prime age” men, or those between ages 25 and 54, don’t have jobs and aren’t looking for one. That’s up from 8 percent in the late '90s, according to the Bureau of Labor Statistics. (The women’s rate, meanwhile, is up slightly less but since 2007 has crept up in parallel with the men’s.)

Over the same period, more people started taking painkillers in the United States. Sales of prescription opioids quadrupled. Overdoses have spiked. Some employers, desperate for workers, have even done away with drug screens.

Nationwide, the slow decline in employment also comes from retiring workers and more young ones heading into college, rather than directly into jobs. Automation, too, is reducing the demand for lower skilled workers, which could further exacerbate the downswing.

Employment trends among prime age men are particularly troubling: 69 percent are employed today, a sharp descent from 75 percent in 2000. Women have less dramatically spiraled downward, with 57.2 percent working now, a drop from the early aughts’ 60 percent.

Read more: