Now that we're getting deeper into earnings season, investors have begun to focus more of their attention on what really matters: earnings. Other than Monday's drop, which was caused by the poor gross domestic product numbers from China, all week we saw stocks trading on earnings news more so than on economic data. And in that kind of environment, when earnings disappoint, stocks fall. That's what we saw happening all around the market this week, and it's why the major indexes moved lower over the past five trading sessions.

The Dow Jones Industrial Average (DJINDICES:^DJI) lost 317 points, or 2.16%, and now sits at 14,547 after 19 of its 30 components ended the week lower. The S&P 500 didn't perform much better, losing 2.11%, while the Nasdaq ended the week as the biggest loser, after dropping 2.69%.

Before we hit the Dow losers, let's look at the index's big winner. Coca-Cola (NYSE:KO) ended the week higher by 3.84%, even after it fell 2.41% on Monday alone. Monday's decline was probably due to an overreaction from shareholders relating to China's slowing GDP. The stock quickly turned things around and rose 5.69% on Tuesday, after the company reported better-than-expected revenue and earnings for the first quarter. Earnings per share beat analysts' estimates by $0.01 after coming in at $0.46 per share, even though revenue fell 1% to $11.04 billion, which was higher than the $11.02 billion Wall Street had expected.  

The big losers
The release of China's GDP numbers hit nearly the whole market on Monday, but most stocks rebounded. A few, however, continued to fall as the week progressed, and one of them was Caterpillar (NYSE:CAT). Shares of the construction heavy-equipment manufacturer fell 5.43% this past week. After losing just less than $2 per share on Monday, it dropped another dollar on both Tuesday and Thursday.

Caterpillar releases earnings on Monday, and it will probably be another volatile day for shares. If the company misses, expect another big decline, but if Cat beats Wall Street's expectations, shares are likely to climb rapidly higher. For more about what to expect from Monday's earnings report, click here

Shares of UnitedHealth Group (NYSE:UNH) lost 4.74% this past week. The stock tumbled 3.7% on Thursday alone, after the company announced an earnings report in which it beat on the bottom line and missed on the top. But what hit the stock perhaps even harder was the announcement that a major public-sector employer had reduced its coverage from a full-risk plan to cheaper fee-based coverage. This may be a new trend the health-insurance companies will begin seeing, and if that's the case, it will most definitely hurt revenue and profits.  

And the biggest Dow loser this week was IBM (NYSE:IBM), as shares dropped 10.11% over the past five trading days. The biggest decline came on Friday, when the stock fell 8.28% after the company announced earnings for the first quarter and announced that it missed on both the top and bottom lines. Analysts wanted to see revenue of $24.62 billion and earnings per share of $3.05, but IBM managed to bring in only $23.41 billion in revenue, resulting in bottom-line EPS of only $2.70. Investors clearly were disappointed with the results, but the bigger question is whether this is just a one-time fluke for IBM. Is the company is losing its luster? Investors will have to follow IBM over the next few quarters to find out, but be prepared for some volatile days ahead.

Other Dow losers this week:

Fool contributor Matt Thalman owns shares of Bank of America and JPMorgan Chase. 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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