The Dow Jones Industrial Average (INDEX: ^DJI) fell 0.4% this week, with most of the pain coming yesterday after there was some doubt raised as to whether Greece would receive its latest batch of bailout money.

Investors fear that failure to bail out Greece would leave an overleveraged financial system on the hook, triggering -- surprise, surprise -- a financial crisis.

But some stocks did even worse than others. These were the three worst performers:

Company

Weekly Price Change

Alcoa (NYSE: AA) (4.4%)
Caterpillar (NYSE: CAT) (1.9%)
Boeing (NYSE: BA) (1.8%)

Why, you ask, did shares of these three companies decline?

Shares of Alcoa plunged yesterday, along with the general market's decline. As a volatile member of an economically sensitive industry, Alcoa's stock tends to amplify the performance of the broader market. But there were also a few specific pieces of bad news for the aluminum market. Reuters issued a negative report on aluminum. Rio Tinto (NYSE: RIO) reported a 59% decline in its quarterly earnings on a major writedown of its Canadian aluminum assets. And Bloomberg reported that aluminum traders probably have closed out bullish bets on the metal.

Caterpillar is largely in the same cocoon as Alcoa. Both have enjoyed outsized gains (about 20%) so far in 2012 on the basis of improving economic news. When investors take a breather from their economic optimism, these two will be among the hardest hit. That's because demand for construction equipment is especially economically sensitive -- why order expensive new construction cranes when you're unsure of demand for construction? Moreover, they're capital-intensive to produce, so Caterpillar uses significant balance-sheet leverage for such a cyclical industry (about 2.5:1).

Last up: Boeing. Although it turns out its 787 Dreamliner planes would need additional inspection on Monday, the aircraft maker said it'll still be able to meet its 2012 delivery dates. The planes are nearly three years behind schedule, and on Thursday Air India raised its demand to $1 billion as compensation for the delays. Add that to the general market anxiety on Friday, and it's not hard to come up with a 1.8% decline for the week.

Although Alcoa, Caterpillar, and Boeing were the worst performers in a rare down week for the Dow, it's important for us to remember that it's long-term performance -- not daily or even weekly 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 term, 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 for free.