Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

It has already been a bit of a choppy day for the markets, and it's only 12:45 p.m. EDT:

^DJA Chart

^DJA data by YCharts.

At the time of writing, the major indexes are mixed, with the Dow Jones Industrial Average (INDEX: ^DJI) up 5.32 points, or 0.11%, the S&P 500 down just two points, or 0.13%, and the Nasdaq falling 23 points, or 0.87%.

Why the fluctuation? Investors remain concerned about the government shutdown and the debt ceiling debate, as well as the announcement from the White House that President Obama will nominate Federal Reserve Vice Chairman Janet Yellen to replace retiring Ben Bernanke as chairman. The markets believe Yellen will follow closely in line with Bernanke's footsteps and continue the Fed's accommodative monetary policies.

But, despite what is being seen as good news, there are still a few losers within the Dow worthy of a look.

Shares of Merck (NYSE: MRK) are down by 1.1% after Credit Suisse began coverage on a handful of pharmaceutical companies, giving Merck a "neutral" rating. Meanwhile, Pfizer (NYSE: PFE) was labeled "outperform." Credit Suisse wrote that while Pfizer will benefit from its shareholder-friendly capital-allocation policies and emerging specialty pipeline, the company's restructuring plans will take another two to three years to be fully realized. That long of a timeline may be causing some investors to flee to a stock with a closer timeline for growth.

As for Merck, Credit Suisse wrote that the company's top-line growth is flat, and while the company has a number of opportunities in the future, it will all come down to whether or not Merck's management can execute on them. Regardless of what one analyst believes may or may not happen for a company in the future, the average investor needs to remember that this is just the opinion of one or two people -- no more than an educated guess as to what may happen in the coming days, months, or years. So we shouldn't put too much stock in each prediction or too much money behind a single call.

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Fool contributor Matt Thalman has no position in any stocks mentioned. Check back Monday through Friday as Matt explains what caused the Dow's winners and losers of the day, and every Saturday for a weekly recap. Follow Matt on Twitter @mthalman5513

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