The shrinking percentage of men in the workforce is one of the economy's biggest mysteries. What's to blame? Here's everything you need to know:

How many men aren't working?
More than 7 million men between the ages of 25 and 54 — prime working age — have dropped out of the labor force. That means they're not only unemployed but have also given up looking for a job. Shortly after World War II, virtually every man of prime working age was either working or looking for work. But the labor force participation rate for men has been declining steadily since the mid-1960s, from almost 97 percent to about 88 percent today. There is a smaller percentage of men working now than in 1940, near the end of the Great Depression, when the overall unemployment rate was above 14 percent. Nicholas Eberstadt, an economist at the conservative American Enterprise Institute, has called the case of the missing men a "quiet catastrophe," forgotten amid the broader story of America's economic recovery since the financial crisis. "It is well past time for America to recognize the collapse of work for men as the grave ill that it truly is," he says.

Why aren't they working?
There is no one single reason. Men have been dropping out of the workforce at roughly the same rate for the past half century, through boom times and recessions alike. The decline in manufacturing jobs has almost certainly played a role. In 1970, more than a quarter of American workers, most of them men, had jobs in factories. Today, it's fewer than one in 10. Nevertheless, only one in seven men outside the workforce says a lack of available jobs is the reason he's not working. Another problem is the explosion of America's prison population. By some estimates, 12 percent of adult men have been convicted of a felony, not including those currently imprisoned. Employers are reluctant to hire ex-cons, so many of these men have found themselves virtually unemployable.

Who supports them?
Their families and taxpayers. About 57 percent of men outside the workforce received some form of disability benefits in 2013, according to the Census Bureau. Overall, the number of Americans receiving disability has doubled to 8.8 million people since 1996, costing the federal government $260 billion per year. The U.S. now spends more on disability insurance than on food stamps and welfare combined. For others, especially younger men, it's often relatives who pick up the slack. Some 70 percent of lower-skilled men in their 20s who didn't have a job lived with a parent or close relative in 2014.

How are these men doing?
Not well. It isn't clear whether pain and sickness keep people out of the workforce, or if being out of work makes people sick, but nearly half of them report taking a painkiller every day. About two-thirds of the men taking pain medication were using prescription drugs — contributing to the nationwide opioid addiction epidemic that causes 78 deaths every day, from overdoses on pills and heroin. About 20 percent of the men say they have difficulty walking or climbing stairs; about 16 percent report memory or concentration problems.

What do they do all day?
While women who aren't in the labor force often work in other ways, raising children or caring for relatives, only 28 percent of men without jobs have a child under 18 living with them. Men who drop out of the labor force gain an extra 2,150 hours of free time each year, and they devote a good chunk of it to watching television and movies — in 2014, an average of 5.5 hours a day. Younger men also spend lots of time playing video games (see below). A society with so many idle men, warns liberal economist Larry Summers, is unlikely to "maintain communities or have happy, cohesive families. As we are seeing this fall, such a society is prone to embrace toxic populist policies."

What can be done?
If current trends hold, a quarter of prime-age men will be out of the workforce by 2050, making the economy less productive. It will also mean generations of men will be sicker and poorer than their peers in the workforce. Presidential candidates Hillary Clinton and Donald Trump have both proposed massive infrastructure spending programs, which would at least temporarily replace lost blue-collar jobs. Job training and apprenticeship programs could also target the 85 percent of men outside the workforce who don't have bachelor's degrees. Liberal economists have called for wage insurance that would subsidize lower-paid work that some men see as beneath their dignity. In one survey of unemployed men, 44 percent said there were jobs near them they could get but didn't want to take. But a cultural shift might also be necessary. Many growing service sector professions are so-called pink collar jobs, traditionally dominated by women, such as nursing and teaching. Conservatives would like to see entitlement reform linking disability benefits to job training, similar to welfare reforms in the 1990s. "Why haven't we had the same sort of conversation about stigmatizing or shaming unworking men that we had 20 years ago about mothers on welfare?" Eberstadt asks. "They were not idle; they had little kids."

Living in an alternative reality
Could video games be luring men out of the workforce? Economist Erik Hurst at the University of Chicago found that young men without college degrees have replaced 75 percent of the time they would have spent working with time spent on the computer, mostly playing games. But while depression is a serious problem for the missing male workers, young men who aren't in college report being happier than they were in the 2000s. It may be that living in virtual realities distracts men from their deeply unsatisfying lives — but it also lessens their incentive to hunt for work, take less prestigious jobs, or make big changes in their lives. "When I play a game, I know if I have a few hours I will be rewarded," said 22-year-old Danny Izquierdo of Silver Spring, Maryland. "With a job, it's always been up in the air with the amount of work I put in and the reward."