If there is one formula that we all subscribe to — Republicans, Democrats and Independents, alike — it is this: a strong economy equals happiness and, conversely, a weak economy equals unhappiness. There's only one problem: It's not true.

America is four times wealthier than it was in 1950, yet we are no happier, according to many surveys. Wealth, it turns out, is subject to the law of diminishing returns. Beyond a certain point, it takes a lot more money to make us just a little bit happier.

Look, I realize that if you've lost your job, or your home, or your 401k has taken a big hit, you're not likely to be happy. But for most of us, that is thankfully not the case. We might be anxious about the economy, worried, but that doesn't mean we're miserable.

It takes a lot to shake our national happiness. The attacks of Sept. 11, horrific as they were, did not do so, according to surveys conducted shortly afterward. If there is such a thing as a happiness bubble, it is a much tougher, resilient bubble than the stock and real estate ones that have burst recently.

So, if it's not material prosperity, what makes us happy? Study after study has found that the answer is — in two words — other people. Warm, caring relationships; high levels of trust; strong families. None of which, of course, has anything, to do with the Dow or the NASDAQ or — our favorite economic barometer — Gross Domestic Product.

GDP is the sum of all economic transactions in a given year, a giant national cash register that tallies everything. Everything, except — in the words of Robert Kennedy — "the beauty of our poetry, or the strength of our marriages or the intelligence of our public debate."

A few countries recognize this mismatch and are trying to do something about it. The tiny Himalayan Kingdom of Bhutan has implemented a policy of Gross National Happiness.

The French and even the dour British are also exploring ways to come up with a national happiness index. There's no reason why we couldn't do the same. It's far from infallible — happiness being such a slippery, subjective thing — but it would do no harm.

I can envision a day when, along with the Dow and the GDP, the NHI, or National Happiness Index, flickers across our TV screens. Perhaps then we'll realize what we've known all along: it's the only number that really matters.

Eric Weiner is the author of The Geography of Bliss: One Grump's Search for the Happiest Places in the World.

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