After a slew of earnings reports, the Dow Jones Industrial Average (INDEX: ^DJI) gained 1.6% this week.

But three stocks lagged behind the others:

Company

Weekly Price Change

Wal-Mart (NYSE: WMT) (5.5%)
Procter & Gamble (NYSE: PG) (4.5%)
Caterpillar (NYSE: CAT) (2.9%)

So what's going on with these companies?

Wal-Mart
Shares plunged afterThe New York Times revealed that the discount retailer had been systematically bribing Mexican officials to speed up approval of new store construction to get an advantage over competitors. The allegations aren't particularly surprising, per se; what makes the 8,000-word piece so damaging is its thorough documentation of the bribes as well as the cover-up that seemed to extend up through the highest reaches of Wal-Mart management and how vital Wal-Mart's Mexican operations have been to its growth.

Procter & Gamble
P&G reported a 16% decline in its net income, which wasn't actually as bad as analysts had expected. But investors are more concerned about the company's prediction that weak growth in developed economies, Venezuelan-mandated price cuts, and rising costs could pressure full-year earnings.

Caterpillar
Caterpillar reported a 29% surge in earnings, in large part because of its acquisition of Bucyrus. Although that topped analyst forecasts, it wasn't enough for investors. Weakness in the market for construction equipment in Brazil and China meant that Cat sales came in lower than analysts had expected.

Wal-Mart, P&G, and Caterpillar were the worst performers this week, but it's important for us to remember that it's long-term performance, not daily price fluctuations, that ultimately matter to investor returns. If you're interested in one stock that our chief investment officer picked to crush the market over the long haul, check out our brand-new report, "The Motley Fool's Top Stock for 2012." It highlights a company that is revolutionizing commerce in Latin America. For a limited time, you can get instant access to the name of this company -- and it's free

Ilan Moscovitz doesn't own shares of any company mentioned. You can follow him on Twitter, where he goes by @TMFDada. Motley Fool newsletter services have recommended buying shares of Procter & Gamble. Motley Fool newsletter services have recommended creating a diagonal call position in Wal-Mart Stores. The Motley Fool has a disclosure policy. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. Try any of our Foolish newsletter services free for 30 days.