"The second quarter is going to be much stronger than the first for the reasons we all know, the weather. Investors are trying to decipher whether this improvement is a weather-related bounce or if there's actually internal growth happening," said Bucky Hellwig, senior vice president at BB&T Wealth Management in Birmingham, Alabama.
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The U.S. economy contracted at a 2.9 percent annual pace in the January-March period, its worst performance in five years.
Recent jobs and other economic data suggest the economy was growing briskly heading into the second half, with growth forecasts for the second quarter now topping a 3 percent annual pace. June's payrolls report showed a surge in job growth and the jobless rate closing in on a six-year low.
One promising sign for the second quarter: typically pessimistic analysts' forecasts, which most S&P 500 companies still tend to beat, declined just 2.2 percentage points between April 1 and July 1.
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That is the smallest overall decline since the first quarter of 2011, Thomson Reuters data showed, and about half the average decline seen in the last five years.
Mike Jackson, founder of investment firm T3 Equity Labs in Denver, said his research shows eight out of the 10 S&P 500 sectors—all but staples and utilities—should post surprises this quarter.
"It probably suggests the earnings increases are occurring across a broader sector of the economy than what was previously believed," he said.
GE's quarterly report on Friday showed the profit margin for its industrial businesses, a closely watched barometer by Wall Street, expanded 0.2 percentage point to 15.5 percent.
To be sure, not all reports are positive. Container Store Group and Lumber Liquidators both warned about upcoming results, suggesting that retail weakness remains.