Hard to see why everyone gets so excited about gross domestic product data. The stock market surged Thursday after the pre-opening announcement that the economy had grown 3.5% in the third quarter. But why?

Is anyone really surprised by the announcement, in the closing days of October, of data on how the economy performed in July, August and September? Do we really need anyone to tell us? Didn't we all live through it? Aren't investors supposed to be interested in the future, rather than the past?

That's how it used to be. Nobody cared, nor should they have. But the world is so uncertain and dangerous now, we have to take seriously every little bit of information that could conceivably bring any sanity to our crazy world.

So let's take a look at the GDP data and try to find something useful -- and something that you haven't already read somewhere else.

What everyone already knows is that the economy grew in the third quarter -- after three quarters of shrinking. And it grew a lot. Three-and-a-half percent is a big number. Not a huge number, especially after three bad ones. But it's good news on the face of it, and not particularly a surprise.

Here's something that surprised a lot of supposedly smart people, and it's very important for what it signals about the future of the economy. In the third quarter, the portion of GDP that constitutes personal-consumption expenditures -- spending on goods and services by consumers -- hit a new all-time record high at 71%.

That's so surprising and important because lots of very influential economic commentators have been saying that, even when the economy recovers, the American consumer won't. There's too much unemployment; too much debt; too much loss of retirement savings in houses and the stock market. How can consumers keep on spending? Well, apparently they can. More than ever.

Well, not exactly. Consumers spent about the same amount this last quarter as they did the same quarter last year. But GDP this quarter was 2.3% lower this quarter than last year. That means consumer spending made up a larger share. In fact, as I said, this quarter it was the largest share in history.

In other words people produced less, but they spent the same amount. What does that tell you? It tells you that even in the tough times we've been through this last year or two, people still want to spend. There's no change in behavior at all.

How does this fit in with all the talk you hear every day in the media about the "new normal" -- the coming generation of sadder but wiser consumers who scrimp and save. Forget the image of the spending-happy consumer. No more BMWs. No more flat-panel TVs. No more lattes. It's a new world of Hamburger Helper for everyone.

It sounds like a great theory. Some very smart people expound it (you can't turn on CNBC without hearing them yammer about it). And apparently it appeals to a Puritanical streak in us that makes us feel guilty about enjoying ourselves while hard-working China becomes the world's economic powerhouse. They expect to see -- no, it's more: they prophesize -- that the consumption share of GDP must fall, as consumers stop spending and instead work and save.

Except that it's just not true, or at least not yet. Maybe next quarter. But then again, that's what the "new normal" yammerers have been saying ever since the recession set in. Yet this is the third quarter in a row in which the consumption share of GDP has moved to new all-time highs.

One thing we have to be careful with here is the effect of the "cash for clunkers" program. There's no doubt that program motivated a lot of auto sales that wouldn't have happened otherwise, and auto sales are part of spending. If we take auto sales out of the mix, spending as a portion of GDP is still at all-time highs.

While the "clunkers" issue doesn t really affect my observations about the consumer, it does affect our overall appraisal of growth in the third quarter. About half the quarter's growth came from auto production. It's hard to know with precision, but surely a great deal of that half came from the "clunkers" program. So it raises real questions about whether the quarter's growth is sustainable.

What will happen next quarter without the program in place? The prospects aren't good. Since so many people bought cars in the last quarter to take advantage of the program, the demand for new cars now is way down -- everyone who wants one already has one. So this quarter's auto sales might be simply horrible.

On the other hand, the people who advocated the "clunkers" program in the first place argued that it would help kick-start the economy. Maybe auto sales themselves would have only a one-time surge, but that surge would get money into circulation throughout the economy, and once money starts circulating the hope is that it will trigger growth everywhere. Maybe -- but I'm a skeptic on that one. Hope is not a strategy.

The same thing goes for housing. In the last quarter we learned that the housing sector grew. Yes, it really did. It's the first quarter with anything other than horrific shrinkage since the fourth quarter of 2005. Does it mean that the housing bust is over? Maybe, maybe not. Don't forget that the first-time homebuyer's credit was in effect in the last quarter. So who knows if there was any real demand -- and even if there was, is there any left?

So the GDP data released yesterday raises as many questions as it answers. Except in the area of consumer spending. There we really have learned something. What we've learned is that there are a lot of things to worry about in this economy, but the consumer isn't one of them.