Job seekers wait in line to enter the Choice Career Fair in San Antonio, Texas, U.S., on Thursday, April 16, 2015. (Matthew Busch/Bloomberg)
Opinion writer

Despite public proclamations and careful positioning to the contrary, Jeb Bush and Hillary Clinton actually agree on at least one major economic issue. Not just any economic issue, either — but one that looks like a defining problem of our time.

I’m talking about the growing number of Americans sitting on the sidelines of the job market.

As Bush explained in a somewhat controversial interview last week, not enough Americans are participating in the job market. On Monday, Clinton echoed his concerns in an ambitious economic policy speech.

“Today, let me emphasize another key ingredient of strong growth that often goes overlooked and undervalued: breaking down barriers so more Americans participate more fully in the workforce, especially women,” Clinton said. “When we leave people out or write them off, we not only shortchange them and their dreams, we shortchange our country and our future.”

Both candidates are correct to worry about this trend. The share of Americans who are either working or looking for work has tumbled for about two decades, with the decline actually accelerating during the current recovery. That is actually one of the key reasons the unemployment rate has fallen so quickly: You get counted as unemployed only if you’re actively looking for work, and a smaller share of Americans happen to be doing so.

Declining labor force participation rates have been blamed on the aging of the workforce, but demographics don’t tell the whole story.

So-called prime-age workers — those between 25 and 54 — are dropping like flies, too. In June, 80.6 percent of people in this age group were in the labor force, down from a high of 84.6 percent at the turn of the century . Men and women have been exiting the workforce in droves, though the outbound trend for men started much earlier.

This is troubling, not only because of the “dignity of work” and other lofty ideals about American ambition and self-actualization. The United States is letting one of its most precious and productive assets — human capital — lie fallow. As Clinton noted in her speech, putting people’s skills and talents to work unleashes economic growth. According to a 2011 study , women’s increased participation in the workforce since 1970 accounts for about a quarter of gross domestic product.

Where Bush and Clinton differ, of course, is in their diagnosis of the causes behind these trends, and therefore in their prescriptions for how to address them.

To Bush (among other Republicans), one key reason so many Americans have ceased looking for work is that they have been lulled into complacency by our hammock of a social safety net . Declining workforce participation rates are basically the result of a coordinated American vacation. The remedy, then, is to make being on the dole much less fun. Of course, we’ve already done this to some extent at the federal level by eviscerating the welfare system . Some states, such as Kansas and Wisconsin , are also independently enacting their own version of such policies, by making poverty and unemployment as unpleasant and shameful as possible.

Clinton comes at the problem from a different premise: that people out of the labor force aren’t hedonistic layabouts; rather, they want to work, but can’t figure out how to fit work into their rest of their lives.

To that end, her solutions rely more on legislating work-life accommodations — that is, “making it easier for Americans to be both good workers and good parents and caregivers.” These include policies such as mandating paid sick and maternity leave, subsidizing child care, and providing predictable and flexible scheduling.

As you can probably tell, I give more credence to Clinton’s approach than Bush’s. But it still remains limited in that it mostly (though not exclusively) addresses the barriers preventing women from working, given that family caregivers are still predominantly female. Men, remember, have been leaving the labor force in large numbers, too, in a trend that predates their relatively recent rise as more active co-parents and caregivers. Their dropout rates are likely due to two main factors: the structural decline of male-dominated industries such as manufacturing and construction, and the fact that so many men have effectively become unhireable because of criminal records.

Don’t get me wrong; I’m delighted to see more attention focused on the barriers to work for women. But I’d still love to hear more, from all the candidates, about how to help more of the men sitting on the sidelines — both for their own good, and for the economy’s.