MENLO PARK, Calif. (CNN/Money) - General Electric's warning on Friday is only somewhat worrisome for GE itself. More problematic is what GE's slippage says about the economy and the upcoming earnings season.

The financial, media and manufacturing conglomerate lowered its full-year expectations again Friday morning, the third cautionary message since June. (Might the mighty GE run the risk of becoming a 'serial warner,' the kind of company whose projections have an annoying habit of slip-sliding away?)

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In June, it hinted of weakness in its plastics business, while outwardly keeping its expected 2003 profit range at $1.55 to $1.70 per share. (The company took pains to claim it was no warning, but I warned that it was.)

Then in July it lowered the range to $1.55 to $1.61, and on Friday to between $1.55 and $1.57.

The primary culprit for GE's (GE: Research, Estimates) warning is weakness in its plastics division. There are other problems, but this is the one CEO Jeffrey Immelt chooses to highlight -- rising oil prices translate into higher raw-material expenses for GE plastics.

What doesn't add up, however, is that GE's plastics unit is a relative pimple on the beast's rear end.

It accounted for just 3.8 percent of third-quarter revenue, and 2 percent of total profit.

Important, sure. But there's got to be more.

The more is the economy. And this gets us back to the perennial question of whether or not GE should be considered a proxy for the U.S. economy. I say the answer is yes.

I also think Immelt is doing a good job of positioning GE, jettisoning lower-growth units and picking up speedier ones. That will pay off one day.

But in the meantime the dial isn't moving much. If GE earns $1.56 per share this year it will have grown earnings a measly 2.6 percent since 2002.

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And if you buy the proxy theory, earnings at other companies selling into the mainstream of global business ought be in the same boat.

Yet the stock market rocks on as if in a full-fledged economic recovery.

Of course, there's been a fair amount of good news. Yahoo! (YHOO: Research, Estimates) jazzed investors with a solid quarter, though that could be dismissed as company-specific. SAP (SAP: Research, Estimates) is a better argument because that software maker caters to the Fortune 500.

Then there's GE, which is bigger, more varied and far more important.

If GE's warning is a harbinger of things to come, it should be an interesting earnings season, to say the least.

Adam Lashinsky is a senior writer for Fortune magazine. Send e-mail to Adam at lashinskysbottomline@yahoo.com.

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