Republican presidential nominee Mitt Romney, as you have all heard by now, has been caught on tape telling a group of campaign donors that his opponent has locked up the votes of the 47% of Americans “who are dependent upon government, who believe that they are victims … who pay no income tax.”

It is true that just over 46% of Americans paid no federal income taxes in 2011. This is the group previously dubbed “lucky duckies” by the editorial writers at the Wall Street Journal. Their share of the population has actually declined during the Obama administration, after hitting 51% in 2008 and 2009, reports the Urban Instite/Brookings Institution Tax Policy Center. But the Tax Foundation has documented a marked growth in their ranks since the mid-1980s, mainly due to new tax breaks created by Congress (with Republicans the driving force behind many of them).

There are lots of other taxes, though, besides the federal income tax. The bottom 20% of the income distribution pay 4% of their income in federal taxes, and another 12.3% in state and local taxes (these numbers come from a Center on Budget and Policy Priorities summing up of data from multiple sources) — giving them an overall tax rate that’s lower than mine but probably not all that different from Mitt Romney’s.

Romney’s comments are part of a broader Republican emphasis this year on the idea that the U.S. has developed a dependency problem. “In a very short period of time,” Romney’s primary opponent Rick Santorum speechified back on Super Tuesday, “a little less than 50 percent of the people in this country [will] depend on some form of federal payment, some form of government benefit to help provide for them.”

That’s about right: in 2011, according to the Census Bureau, 150 million of the 305 million people in the U.S. lived in a household that received benefits (Medicaid, Social Security, food stamps, and Medicare were the Big Four, in order of number of recipients) from the government. These numbers have risen dramatically since the 1960s, Nicholas Eberstadt of the American Enterprise Institute writes in his epic new essay “A Nation of Takers.” The federal government now spends more on Social Security, Medicare, Medicaid, and other entitlements than on all its other activities combined.

This has some clear implications for the long-run fiscal position of the U.S. What’s far less clear, as the University of Maryland’s William Galston argues in response to Eberstadt, is that it really makes the U.S. “a nation of takers.” Actually, many recipients of government aid pay in more in taxes, over their lifetimes, than they receive in benefits.

An aging population inevitably means more recipients of Social Security and Medicare, while the worst economic downturn since the Great Depression can’t help but add to the ranks of those receiving unemployment insurance or food stamps. Most of the increase in entitlement expense is coming from the health insurance programs Medicare and Medicaid — the result as much of an apparently congenital American inability to rein in health care costs as any increase in dependency.

So while Santorum’s 50% is a worrying statistic, it’s not obvious what the policy implications are. As for the political implications, the New York Times reported earlier this year that the greater a county’s dependence on government benefits, the more likely it was to vote Republican in 2008. The states with the highest percentage of income tax non-payers also lean Republican. In other words, the 47% that Romney disparages may actually be his voter base. Or was his voter base.

That’s ironic, but there’s another statistic that I find truly alarming. It’s that 66.6% of Americans aged 15 to 64 had jobs in 2011, according to the Organization for Economic Cooperation and Development. That’s a lot higher than 50%, but it’s down from 74.1% in 2000 — and it’s well below the Netherlands’ 74.9%, Germany’s 72.6%, and the United Kingdom’s 70.1%. In the 1990s, the U.S. had a much higher employment-to-population ratio than any of those nations. Now the tables have turned.

The turnaround has been especially dramatic in Germany, which has made big labor market changes since the 1990s to allow for more flexibility in hiring, firing, and work rules, and to steer the unemployed back into jobs. But Germany also still has a much more generous welfare state than the U.S. — meaning that it’s hard to argue that too-lavish government benefits are the main cause of the falling employment ratio here.

So what is the cause? My guess is an unbalanced, still finance-heavy economy that produces too few middle-income jobs, plus educational and job-training systems that don’t prepare people well enough for the jobs that do exist. There may well be better explanations. I’d love to hear someone offer up a few on the campaign trail this fall. But I won’t hold my breath for that.