– The pickings are slim when Mike Bowling needs to hire someone for his convenience stores in London and Manchester.

"This is the hardest I've ever seen getting workers and keeping workers," said Bowling, who has been in business 18 years. "You just ain't got nobody to pick from."

It's clear to Bowling that Kentucky's drug crisis has affected the workforce, causing higher turnover, bringing additional costs to train new employees and fueling employee thefts.

Recent research bears that out.

In a paper published by the Federal Reserve Bank of Cleveland, economists Dionissi Aliprantis and Mark E. Schweitzer estimated that participation in the labor force by men in their prime working years — ages 24 to 54 — was 4.6 percent less on average in counties with high rates of opioid prescribing than in counties with low prescribing rates.

The estimated effect was even greater among men who had a high school education or less. In that group, the participation rate in the labor force was 7.4 percent less among white men in high-prescribing counties and 9.7 percent less among nonwhite men, the researchers estimated.

The estimates covered the whole country, but hold particular significance for Eastern Kentucky, which has counties with some of the highest opioid prescribing rates in the nation and a relatively low percentage of people in the workforce.

Of the 169 counties in the Cleveland Fed's region, the top 10 in the number of opioid prescriptions per 100 people were all in Kentucky in 2011, and nine were in Eastern Kentucky, according to Fee's report.

Prescribing rates dropped significantly in Eastern Kentucky counties between 2011 and 2016, but remained well above the national rate.

In a separate report issued last month, the Organization for Economic Co-operation and Development cited opioids as a factor in why the labor participation rate in the U.S. was lower in late 2017 than the average of all 35 nations in the group.

The organization said the correlation with nonparticipation "in areas most beset by opioid addiction suggests that addiction ultimately impairs participation."

The research helps explain one factor in the low percentage of people in the workforce in Eastern Kentucky.

A study released in September 2016 said the participation rate in the region was 44.74 percent, compared to 59.8 percent for the state as a whole and 63.9 percent nationally.

The study, supported by a consortium of development groups and colleges, surveyed thousands of workers and employers in 27 Eastern Kentucky counties.

Heather Burton, chief operating officer of Double Kwik, which operates more than 40 convenience store in the region, said she believes the lower number of people in the workforce hinders efforts to hire for entry-level jobs at the stores.

The company starts employees at the stores above minimum wage and offers benefits that include paid vacation and a 401(k) program, but some stores still have difficulty hiring, Burton said.

"We do have shortages," she said.