The Dow Jones Industrial Average (INDEX: ^DJI) is probably the best known stock-market measure in the world. But that doesn't mean it always goes the same direction as the overall stock market. Today, we saw that fact in action, as the Dow lost 31 points even as the S&P 500, Nasdaq Composite, and Russell 2000 small-cap indexes all gained ground. As Fool contributor Travis Hoium noted earlier today, the beginning of earnings season next week is starting to weigh on the market, as investors prepare for a potential year-over-year drop in S&P 500 earnings for the first time in several years.

The Dow's biggest movers were on the down side today. DuPont (NYSE: DD) led the losers with a 1.7% decline, as rival Mosaic (NYSE: MOS) reported weaker-than-expected earnings this morning. With both companies serving the agricultural space, Mosaic's results raise questions about whether DuPont's success in the segment will continue. Mosaic fell almost 4%.

McDonald's (NYSE: MCD) also shed ground, dropping 1.2%. The decline follows on the heels of an analyst downgrade yesterday, but international economic conditions also cast a shadow on the fast-food giant's long-term prospects. With McDonald's relying on overseas growth, it needs economies around the world to buck up and keep expanding.

Finally, Procter & Gamble (NYSE: PG) lost almost 1%. Activist investor Bill Ackman commented on the stock earlier today, pointing to its long-term potential but mourning the missteps that P&G has made in recent years. Although Ackman has been critical of CEO Robert McDonald, he said the board seems committed to giving McDonald a chance to help P&G recover.

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