By any historical measure, the second-quarter earnings season and the outlook for profit growth in the second half of the year is remarkable.

Despite some high-profile misses from the likes of Amazon ( AMZN) and Microsoft ( MSFT), about 70% of S&P 500 companies have so far surpassed analysts' estimates, and earnings are on track to grow more than 20% for a fourth consecutive quarter. A string of gains like this has only been seen four times over the past 50 years, according to Thomson First Call.

"Everyone's trying to do a story these days about how earnings are weak," said Gint Rimas, a senior analyst at Thomson. "I don't know if that's the case."

Companies in the S&P 500 are beating analysts' expectations by 4 percentage points, Rimas said, which is about a percentage point above the average surprise factor. In addition, estimates for the third quarter have actually been revised up overall. Typically, analysts have to lower their overly optimistic estimates around this time.

Judging by the action in the stock market lately -- the Nasdaq is sitting at its lowest level of the year and the Dow is below 10,000 for the first time in two months -- you'd think earnings were about to fall off a cliff. In fact, this year's expected earnings growth of almost 15% in the third quarter and 15.6% in the fourth would be well above normal.

Still, it's hard to argue that investors are acting irrationally.

Expectations for the second quarter had been extremely high and while the news has been very good, it hasn't been quite as good as it was in the first quarter when companies were beating estimates by almost 8 percentage points.

General Motors ( GM) is a good example of a company that breezed past the consensus estimates in the second quarter but still managed to disappoint. Although the automaker's earnings were 12 cents a share better than analysts' had expected, that was nowhere near the 47-cent upside surprise reported in the first quarter. What's more, GM chose not to raise its annual guidance, as it had done in the first three months of the year.

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