In 1910, Henry Van Dyke wrote "The Spirit of America," which opened with this: "The Spirit of America is best known in Europe by one of its qualities - energy."

This has always been true. Americans have always been known for their manic dynamism. Some condemned this ambition as a grubby scrambling after money. Others saw it in loftier terms. But energy has always been the country's saving feature.

So Americans should be especially alert to signs that the country is becoming less vital and industrious. One sign comes to us from the labor market. As my colleague David Leonhardt pointed out recently, in 1954, about 96 percent of American men between 25 and 54 worked. Today it's around 80 percent. One-fifth of all men of prime working age are not working.

Figures from the Organization for Economic Cooperation and Development show the United States has a smaller share of prime-age men in the work force than any other G-7 nation. The number of Americans on permanent disability rolls, meanwhile, has steadily increased. Ten years ago, 5 million Americans collected a federal disability benefit. Now 8.2 million do. That costs taxpayers $115 billion a year, or about $1,500 per household. Government actuaries predict the trust fund that pays for the benefits will be depleted within seven years.

Part of the problem is human capital. More American men lack the emotional and professional skills they need. The Bureau of Labor Statistics reports 35 percent of those without a high school diploma are out of the labor force, compared with less than 10 percent of those with a college degree.

Part of the problem has to do with structural changes in the economy. Sectors like government, health care and leisure have grown, generating jobs for college grads. Manufacturing, agriculture and energy haven't been generating more jobs, as companies use machines or foreign workers.

The result: Probably more men are idle now than at any time since the Great Depression. This time the problem is mostly structural, not cyclical. They will find it hard to attract spouses. Many will pick up habits that have a corrosive cultural influence on those around them. The country won't benefit from their potential.

This is a big problem. It can't be addressed through the sort of short-term Keynesian stimulus some on the left still fantasize about. It can't be solved by simply reducing government, as some on the right imagine.

Attacking the problem will probably require a broad menu of policies: expanding community colleges and online learning; changing the corporate tax code and labor market rules to stimulate investment; adopting German-style practices like apprenticeship programs, wage subsidies and extending jobless benefits for six months if you start a small business.

Bringing the missing fifth back into the labor market and using their capabilities will require money. If this were a smart country, we'd be debating how to shift money from programs that provide comfort toward those that spark reinvigoration.

But, of course, that's not happening. Discretionary spending is declining. Health care spending is expanding. Attempts to take money from health care for other uses are crushed.

There are basically two ways to cut government health care spending. From the top, a body of experts can be empowered to make rationing decisions. This is the approach favored by President Barack Obama and used in many countries. Alternatively, at the bottom, costs can be shifted to beneficiaries with premium supports to help them handle the burden. Different versions of this approach are embodied in the Dutch system, the prescription drug benefit and Rep. Paul Ryan's budget.

We'll probably need a mixture of approaches to figure out what works. Instead, Republicans decry the technocratic rationing model as "death panels." Democrats are in demagogic overdrive about "privatization" or "the end of Medicare."

Let's be clear about the effect of this mendacity: We're locking the nation's wealth into the Medicare program and closing off any possibility that we might do something significant to reinvigorate the missing fifth.

Next time you see a politician demagoguing Medicare, ask: Should we be using our resources in the manner of a nation in decline or one still committed to stoking the energy of its people and continuing its rise?