The sky isn't falling, exactly. America isn't on a fast track to irrelevance. Even in a state of total neglect, we could probably shamble along as a disheveled superpower for a few more decades.

But all empires end, and the warning signs of American decline seem to be blinking more consistently. In the latest annual "prosperity index" published by the Legatum Institute, a London-based research firm, the United States ranks as the ninth most prosperous country in the world. That's five notches lower than last year, when America ranked No. 4. The drop might seem inconsequential, especially in the midst of a grueling recession—except that most of the world has endured the same recession, and other countries are bouncing back faster.

China and India have recovered smartly from the recession, for example. Brazil seems to be barreling ahead. Australia is growing faster than expected, prompting worry among government officials who fear they may have overstimulated the economy. The United States, meanwhile, is muddling through a weak, jobless recovery, and we have a lot of problems that could make prosperity feel elusive for a long time.

Real household income in America has flat-lined, for instance, which means many middle-class families are barely keeping up with inflation. The exploding federal deficit hamstrings the government's ability to help. Healthcare is too expensive, America's manufacturing base is eroding, and two open-ended foreign wars are draining the national treasury. This is not a recipe for building national wealth.

There are still millions of diligent, innovative Americans who could help the nation dig out of its hole. But overall, the American population is falling behind, by a variety of measures. Here are some of them:

Jobs. The International Monetary Fund predicts that the U.S. unemployment rate will be 9.3 percent for all of 2010. That's lower than in some European nations, but it's higher than in Canada and a lot worse than most countries in Scandinavia and Asia. Overall, the U.S. unemployment rate is about average for advanced economies and likely to stay that way. It could be worse, but middling job creation isn't a sign of global leadership.

Economic growth. The IMF also predicts that the U.S. economy will grow 1.9 percent in 2010. That's a tad better than the average for all advanced economies, but at least 10 developed nations will grow faster. Woo-hoo. Three cheers for mediocrity.

Poverty. The U.S. poverty rate, about 17 percent, is third worst among the advanced nations tracked by the Organization for Economic Cooperation and Development. In that sample, only Turkey and Mexico are worse.

Education. American 15-year-olds score below the average for advanced nations on math and science literacy. But don't worry, our nation's future leaders are still ahead of their peers in Mexico, Turkey, Greece, and a few other places.

Competitiveness. In the latest global competitiveness report from the World Economic Forum, the United States fell from No. 1 to No. 2. Sure, let's console ourselves that the No. 1 country, Switzerland, is a tiny outlier nation and that getting bumped from the top spot doesn't really mean anything. Add an asterisk, and we're still No. 1.

Prosperity. The most prosperous nations, according to the Legatum report, are Finland, Switzerland, Sweden, Denmark, and Norway. These fairly homogenous European countries are the teachers' pets of global rankings, often appearing near the top because of right-sized economies and a relatively small underclass. For a huge economy like America's, a No. 9 ranking is still respectable. And part of the drop from last year's No. 4 spot is a change in methodology that puts more emphasis on the health and safety of citizens. Still, in the index's subrankings, the United States isn't even in the top 10 for economic fundamentals, safety and security, or governance. We should do better.

Health. In the Legatum study, the United States ranks 27th for the health of its citizens. Life expectancy in America is below the average for 30 advanced countries measured by the OECD, and the obesity rate in America is the worst among those 30 countries, by far. And, of course, we spend far more on healthcare per person than anybody else—but get no bang for the extra buck.

Well-being. In the United Nations' Human Development Index, which attempts to measure the overall well-being of citizens throughout the world, the United States ranks 13th, one notch lower than in the prior set of rankings. Norway, Australia, Iceland, and Canada are at the top.

Happiness. The United States ranks 11th in the OECD's measure of "life satisfaction"—behind Denmark, Finland, the Netherlands, and other usual suspects. That's not bad, but the United States is one of only five countries where life satisfaction is going down, not up. The other downer nations are Portugal, Hungary, Canada, and Japan. Plus, the research behind these rankings predates the recession, so it's likely that Americans are a lot less satisfied these days.

The overall portrait of America isn't exclusively gloomy, and in some areas we still seem to have an important edge. The Legatum prosperity index, for example, ranks America first for entrepreneurship and innovation. And in a GfK Roper survey of how nations rate as global "brands," America rocketed from No. 7 in 2008 to No. 1 in 2009, largely because the world cheered the election of Barack Obama as U.S. president. But a brand-name leader can't just strong-arm his nation back to greatness. He needs a lot of help from educated, healthy, and employed citizens determined to spread the wealth.