First-quarter GDP numbers were released today, and if you didn't know any better you'd think the country was back in recession mode. The U.S. economy grew at just a 0.1% pace in the first quarter, far below the 1.1% economists were expecting. But shareholders of Express Scripts (NASDAQ:ESRX), Exelon (NYSE:EXC), and Marathon Oil (NYSE:MRO) had bigger things to worry about, as each stock ended near the bottom of the S&P 500 Index (SNPINDEX:^GSPC) today. The S&P, for its part, shrugged off the bad economic omen, adding 5 points, or 0.3%, to end at 1,833.

Shares of Express Scripts tumbled 6.2% as the health care plan provider gave stockholders nothing but a heavy dosage of dreadful news. It started off by reporting first quarter sales and earnings that missed Wall Street expectations. While the company's net income was about 3% below forecasts and revenue missed by a meager 0.5%, it also guided full-year earnings per share lower and announced that it was under investigation by the Feds. This, by almost any standards, was destined to be a very poor day in the stock market for Express Scripts. CEO George Paz stood up for the company, saying he was confident that investigations into the company's relationship with drugmakers would clear it of any wrongdoing.

Exelon Corporation also ended as one of Wednesday's biggest laggards, falling 3.2% in trading. The power utility bought Pepco, making Exelon the largest power distributor in the U.S. Usually acquiring companies see their stock prices fall when they offer to snatch up a competitor, since they're usually forced to pay a steep premium and invest significant resources in the acquisition, so today's plunge isn't anything out of the ordinary in that regard. A takeover of Pepco increases Exelon's exposure to government-regulated markets, making the combined company's cash flows more predictable, a move some investors saw as overly conservative and restrictive to future growth. 

Source: company website

Finally, shares of oil and natural gas company Marathon Oil dropped 2% on Wednesday, as oil and natural gas prices took a dive. Oil fell 1.5% and natural gas was down 0.3% today. Part of the stock market's reluctance to accept the Pepco deal had to do with the fact that the incredible affordability of natural gas has driven energy prices to unsustainably low levels. By keeping its beak wet in unregulated markets, Exelon could participate in a resurgence in energy prices. However, Marathon Oil is a prime example of how too much exposure to unregulated markets can work against you, since results are more prone to rising and falling energy prices. 

John Divine has no position in any stocks mentioned. You can follow him on Twitter, @divinebizkid, and on Motley Fool CAPS, @TMFDivine.

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