The Dow Jones Industrial Average (INDEX: ^DJI) fell hard out of the gate this morning and then slowly recovered ground throughout the day before still ending down 0.79% by market close. That was better than both the S&P 500 (INDEX: ^GSPC) and the Nasdaq, which were down 0.89% and 1.2%, respectively.

What was it that had markets running for the hills today? Europe. Again. Sound familiar? It's the same tune we've been hearing all year, just with a different tempo. Yields on Spanish bonds rose to 7.5% in midday trading, a seriously dangerous level considering Spanish officials have said that anything above 7% is unsuitable for them to effectively recover. Not only that, but Europe's favorite whipping boy, Greece, now appears closer than ever to exiting the eurozone.

The big loser
In concert with poor news from Europe, McDonald's (NYSE: MCD), which counts Europe as its largest market by revenue, fell 2.88%, making it the worst-performing stock on the index today. Even despite soaring past analysts' expectations for European same-store sales, the company still counted the region as the reason for its underperformance, with foreign exchange pressure taking a full $0.07 from earnings. Without the foreign-exchange woes, McDonald's would have actually beaten analysts' expectations of $1.37 per share. Instead, they came in at $1.32.

What this means for the Dow
As an index, the Dow Jones Industrial Average is perhaps the most sensitive to global headwinds. Each component is a massive blue chip that cut its teeth domestically and now has some measure of direct or indirect global exposure. This is more true for some components, like McDonald's, than others. Cisco (Nasdaq: CSCO) recently got nailed for its European position as well, as investors effectively predicted a cutback on business spending and cut shares in response.

This exposure is a reality for investing in these companies. Long-term investors need to both brace for the unpredictable headwinds, and embrace the inevitable tailwinds. Looking to the Dow in particular, some components such as Boeing, Caterpillar (NYSE: CAT), and DuPont have significant European exposure and collect 14%, 22%, and 29% of their revenue from the region, respectively.

Currencies will swing up, and they will swing down. Right now the euro continues to slide against the U.S. dollar, making those segments artificially weaker for these companies and taking a bite out of earnings. But the patient investor knows that at some point weak currencies strengthen and strong currencies weaken with the natural ebb and flow of economies. If you're looking at investing in any Dow component today, make sure you're aware of each company's exposure to weak markets like Europe, and slowing markets like China. Right now, a U.S.-biased company may be the safest place for your money, but over the long run these pressures will ease and great companies will continue to be great investments. That's why I'm not particularly worried as a shareholder of McDonald's and am willing to wait out the company's significant European position.

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