“Every time the economy gets better, the police have a problem recruiting,” said Nelson Lim, executive director of the Fels Institute of Government at the University of Pennsylvania. “It’s like clockwork.”

A blossoming job market means more career choices, said Darrel Stephens, executive director of the Major Cities Chiefs Association. Police departments can’t always keep up with perks other professions in the private sector may offer, he said. “Salary and benefits have declined in many departments,” he said.

The Bureau of Labor Statistics puts the growth rate for “Police and Detectives” as “slower than average” at 4 percent with the average growth rate at 7 percent for other professions. The bottom tenth-percentile for an officer’s salary is $33,430, according to 2015 federal data.

“It’s not an 8-5 job with weekends off,” Stephens said. “The lifestyle is difficult for a lot of people.”