NEW YORK (CNN/Money) - Sure the stock market continues to perform well, but lately things have started to get a little sloppy.

Investors, it seems, are getting harder to please. Where they were happy to bid stocks higher back in December on expectations that fourth-quarter earnings would come in well, now that financial results are landing, investors aren't quite so enthusiastic. A slew of companies that exceeded analysts' estimates by a long shot still saw their shares decline.

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"Companies really have to exceed some high expectations to get rewarded," said Miller Tabak equity strategist Pete Boockvar. "Those that just meet estimates -- it's just not good enough."

If the trend continues throughout the earnings period, it could mark an important shift in the market. The way to win big in 2003 was to buy the riskiest, most beaten down stocks you could find; maybe now investors are getting more discriminating about what they buy.

Although not so discriminating that they're embarking on the long-awaited rotation from economically sensitive stocks into more stable fare. Tech is the best-performing sector in the S&P 500 this year, just like last year. Stocks like Pepsi, which offer steady earnings growth, are down.

Maybe there's a reason for that beyond a typical knee-jerk reaction to buy the sorts of companies that have treated you well. The time to begin to shift out of the more cyclical stocks is when the economy enters the more mature phase of recovery and growth begins to slow.

So far, there are no signs that's happened. Recent economic reports suggest that in the fourth quarter gross domestic product may have grown far more quickly than the 4 percent or so pace economists have penciled in.

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Moreover, points out Citigroup economist Steve Wieting, although the data is scant -- a handful of regional manufacturing reports and consumer confidence surveys -- it appears that the economy accelerated as 2004 began. He forecasts first-quarter growth of 5.5 percent versus average estimates of 4.5 percent.

Wieting's expectation of quicker growth translates into a forecast for higher profits. He sees S&P earnings growing by 14.5 percent in the first quarter over last year and by 15.5 percent.

"Our estimates are higher than company analysts'," he said. "It's the first time that's happened in five years."

If it's true that the economy and earnings are going to be giving Wall Street more upside surprises, it will be more cyclical companies that will be the biggest beneficiaries. The run may not be done.

• Earnings season heats up. Click here to see the company reports that matter most.
• The stock and bond markets are closed Monday in observance of Martin Luther King Day.
• President Bush gives his State of the Union address Tuesday night. Pass the popcorn.
• Economists polled by Briefing.com expect that December housing starts, slated for release Wednesday, will come in at an annualized 1.983 million, down from November's 2.07 million. Building permits are expected to come in at an annualized 1.86 million, down from November's 1.874 million.
• The December index of Leading Indicators, due out Thursday, is expected to climb by 0.2 percent. It gained 0.3 percent in November.