Brock should be in the prime of his life. He’s 31, single, lives in a great city — Chicago — and has a bachelor’s degree and a master’s in computer animation. In any other decade, he’d likely be starting to climb the lucrative incline of the career curve, pulling in promotions and raises, and socking away savings for a downpayment on a house, and eventually, retirement.

Maybe he’d move in with a girlfriend, get married, or start to think about having kids. Or maybe he’d just be hanging out with friends or tearing up Tinder as a bachelor.

Instead, most days Brock doesn’t leave his studio apartment until after noon. He walks to the gym, where he might stay for three hours, running on the treadmill, pumping barbells. He doesn’t talk to anyone, really, except when he has to share a machine or if someone falls off the treadmill. Mostly, he listens to audio books (he likes sci-fi). Finding work was near impossible when he graduated from college in late 2008, and he hasn’t had a job since 2010, when he was working full-time at an Amazon fulfillment center. (He asked that we not use his full name out of concern it would make getting a job more difficult.)

He’s slowly stopped seeing friends out of sheer embarrassment and he just feels uncomfortable around people. He hasn’t dated for years. “I don’t feel confident enough to date anymore,” he told me. “How do you tell someone that you’re 31 and long-term unemployed?”

Brock is one of nearly 3 million American men who need something to do. These men are in their prime working years, age 25 to 54, and want to be employed, but they don’t have jobs and have stopped looking for work. Men’s relationship with the labor market has grown increasingly casual in the last four decades, but the trend has accelerated since the recession. Now, just 89 percent of working-age men are in the workforce, compared to 98 percent in the 1950s, the golden age of the American economy.

“This is an extremely large shift,” said Erik Hurst, an economics professor at the University of Chicago, who has studied the phenomenon closely. “Young men used to always work, and now they’re not.”

There’s no single clear reason the share of men in the workforce has dropped, economists say. But they agree that the implications are huge — on a personal level, for guys like Brock, and for the economy as a whole. If nothing changes, this generation of men will earn less, pay less in taxes, consume more in government services, marry less frequently, and lead increasingly unhealthy lives that lead to earlier deaths.

And since the growth of any economy depends, in part, on the total number of workers in it, the continuing drop in men working and looking for work could make the United States a poorer country over time.

“Our living standards, going forward, depend on how many of these men are participating in the labor force,” said Richard Fry, an economist at the Pew Research Center. “It’s important for the country’s living standards, as a whole, to get them re-engaged.”

Millions of men didn’t stop working overnight. But the problem is more pressing now, because the share of women at work is no longer rising. When the U.S. had millions of women entering the workforce between the 1960s and 1990s, they could pick up the slack as men dropped out. That’s no longer the case.

Getting men to work is important because it doesn’t seem like they’re doing anything much better with their time. In his new book, “Men Without Work,” scholar Nicholas Eberstadt of the right-leaning American Enterprise Institute estimates that men who are out of the labor force gain an extra 2,150 hours of free time each year.

So what do they do? They spend large chunks of time on sleep, grooming and personal care as well as “socializing, relaxing, and leisure,” according to government survey data. That includes five and a half hours a day watching television and movies.

“What is striking, however, is how little of this enormous free-time dividend is devoted to helping others in their family or their community,” Eberstadt concluded.

Before you dismiss these findings as the hand-wringing of a conservative think tank, consider this: The Obama administration largely agrees. A recent report from the White House’s Council of Economic Advisors noted that working-age men who weren’t working — or looking for work — weren’t really contributing much elsewhere. These guys, again, were found to be spending more time on “socializing, relaxing, and leisure,” including watching almost six hours of TV a day.

A separate paper published by Hurst and his colleagues looked at younger, less-educated men ages 21 to 30 who weren’t working or looking for work. They spent large amounts of time on the computer and playing video games, much more than they spent on household chores, exercise, or socializing with friends, among other things.

Oh, and another thing these guys are doing more than others? Smoking and doing drugs, according to the American Enterprise Institute.

That shouldn’t be a surprise. There’s a long-established link between unemployment and drug and alcohol use, although the nature of the link is poorly understood. (Does excess free time lead to drug use, or do users find it tougher to hold onto a job?)

But in recent years, amid the national opioid crisis, that link has become more deadly. In a groundbreaking paper published last year, Princeton University professor Anne Case, and her husband, Nobel Prize-winning economist Angus Deaton, spotlighted a surprising rise in deaths of middle-age white Americans driven by drug-related poisonings, liver disease, and suicides. The uptick in deaths was largest for those with the least education, the group that has fared the worst in the job market in recent decades.

Let’s be clear: Not every guy who has dropped out of the workforce spends his days in a fog of weed smoke and Netflix. No longer the breadwinners, some are instead picking up the kind of unpaid labor that traditionally fell to women.

Take for example Javier, who despite being unemployed in Corona, California, finds himself doing a lot of work. He runs the household, which starts by getting his three kids up, showered, and dressed, starting at 6 a.m. He then fixes school lunches, checks homework, signs permission slips, and loads the kids into his Mazda before dropping them off at their respective high school, middle school, and elementary school. Then he returns home where, before starting on the laundry, dishes, vacuuming, and dinner preparation, he fires up his computer to conduct what’s left of a job search — he had worked in digital and online marketing — that has become increasingly fitful. (Like Brock, he asked that we not use his full name because he worried it would make any job hunt more difficult.)

His wife, an attorney at her family’s practice, is able to support the family on her salary. And Javier does bring in some money by restringing tennis rackets and running a tennis-focused blog. He says they make enough to get by. “It’s just not enough to have a fun life.”

After an hour or so looking at the job listings, he finds himself feeling depressed and useless. It’s a feeling he’s been struggling with more and more lately, prompting him to seek help with a therapist and take some medication. He feels a strain on his marriage as well. “She looks at me like, ‘You’re a fucking jackass,’” he said.

He has continued to send out resumes, checking in with his LinkedIn contacts and looking at job listings. But he says the jobs he finds don’t pay enough to cover the costs of commuting and child care. He feels he’s slowly becoming unemployable. “I’ve been out of work for almost a year,” he said in an interview a few weeks back. “I’m just kind of like, ‘I give up.’”

How millions of other guys came to a similar conclusion is a complex socioeconomic hairball of causes, effects, and consequences. Some, like Brock, have been hurt, in part, by graduating during the worst economic crisis since the Great Depression. Some, like Javier, feel the wages they are being offered just don’t compensate for long commutes, time away from family, and child-care expenses. As for the rest, take your pick: high incarceration rates, the erosion of middle-skill and middle-class jobs, globalization, outsourcing, trade.

Rising numbers of veterans with disabilities and poor health more broadly could also be playing a role. A paper out last week from labor economist Alan Krueger found that nearly half of working-age men who have dropped out of the labor force take pain medication on a daily basis.

All these factors likely play some part in either pulling or pushing men to the fringes or completely out of the job market. And some economists argue that the decline of working men isn’t a crisis but simply a choice.

“One factor to keep in mind is that women are enjoying higher real earnings, making it possible for men affiliated with women to take it easier,” Stanford economics professor Robert Hall told me. “Maybe men have responded to changing conditions in the labor market to take advantage of enjoyable activities at home.”

But many analysts point to a single simple fact: Most of the men who aren’t working don’t have college degrees. And workers without college degrees haven’t gotten much of a raise in decades.

“I think one of the major factors has been work doesn’t pay very much at the low end,” said David Card, an economics professor at the University of California, Berkeley.

According to research from MIT economists David Autor and Daron Acemoglu, real earnings for men without four-year college degrees shrank by an average of 11 percent between 1979 and 2007, whereas earnings of those with bachelor’s degrees, and those with graduate degrees, rose by 10 percent and 26 percent, respectively.

Some of this comes back to the decline of jobs in manufacturing. As recently as 1970, factories accounted for 1 in 4 U.S. jobs. Today, it’s less than 1 in 10. Factory work was heavily male and well-paid, providing a great source of jobs for men who didn’t go to college.

But the share of manufacturing jobs in the U.S. began to shrink in the 1970s, a trend that only picked up steam in recent years as China became, essentially, the workshop of the world. Over the last 20 years, some 5 million manufacturing jobs disappeared as the U.S. economy shifted toward service jobs and felt the impact of foreign trade and technological change.

For a while in the 2000s, these mostly male former factory workers were absorbed into the booming construction industry. But it didn’t last. When the housing boom turned to bust, those jobs vanished too, leaving the pool of workers without bachelor’s degrees without many options. The result? The rates of men at work collapsed. And they haven’t bounced back much.

Economists say there are some things that could be done to get men back to work. A burst of government spending on roads and bridges could help. Compared to the non-college-educated men who are dropping out of the labor force, road- and bridge-construction workers “tend to be men with the similar kind of profile,” Card said.

And unlike most policies economists recommend, this one could actually happen. Hillary Clinton has called for $275 billion in infrastructure spending over five years, paid for in part by higher taxes on the rich. Donald Trump has said he wants to double that.

So, there are reasons to believe that we can still find something for American men to do. After all, we haven’t really tried that hard to fix the problem yet.

Other countries have. The drop in labor force participation in the U.S. has been much worse than in relatively comparable countries such as France, Germany, Canada, and the U.K.

“That tells us that there must be policies that are used, say, in Germany and France and other places around the world that we could learn from and could allow us to get our numbers up,” said David Wessel, director of the Hutchins Center on Fiscal and Monetary Policy at the left-leaning Brookings Institution. “So that tells us we’re not doomed; it’s a reason to be optimistic.”

That’s in part because the United States just doesn’t spend nearly as much on things like job training programs that help keep people in the job market. For instance, Germany spent 0.85 percent of GDP on such policies in 2012, when the U.S. spent just 0.12 percent, according to data collected by the rich-nation research group known as the OECD. The level of U.S. spending is the second-lowest of all countries tracked, just above Mexico.

And of course, there’s always the chance that good old-fashioned economic improvement could help too. The Federal Reserve has been keeping interest rates low for years in an effort to support the economy and bolster the job market.

There has been clear improvement. The U.S. economy has generated jobs for 72 straight months, the longest stretch on record. Unemployment is down from 10 percent in October 2009 to 5 percent in September. (I checked in with Javier last week and he said he had finally had a decent job interview.)

But, don’t kid yourself. There isn’t going to be a single solution. The decline of men at work isn’t just an economic problem; it reflects larger changes in American society.

“I think it’s going to take more than the Fed running the economy hot,” Card said. “I think this is a much deeper and more structural problem.”