BOSTON ( TheStreet) -- U.S. stocks are vacillating between the positivity of strong earnings reports and the negativity of soft economic data. Short-sellers are on the prowl, looking to exploit weakness in heavy-volume names. Here are the 10 most shorted S&P 500 stocks. They are ordered by percentage of float sold short, from heavily shorted to most heavily shorted. If momentum picks up, these stocks could be susceptible to a short squeeze.

10. CMS Energy ( CMS) is a utility in Michigan. Its stock has gained 28% during the past year, outpacing the Utilities SPDR ( XLU), which is up a more modest 7%. Second-quarter net income increased 6.5%, but earnings per share more than doubled to 39 cents. Revenue increased 9.1%. The stock trades at a price-to-projected-earnings ratio of 11, a 14% discount to its peer average. It offers a 3.7% dividend yield with a safe payout ratio of 51%.

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