Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

The major indexes all had a good November, with the Dow Jones Industrial Average (DJINDICES:^DJI) gaining 3.01%, or 470 points, the S&P 500 increasing by 2.5%, or 44 points, and the Nasdaq rising 3.51%, or 137 points. The Dow and S&P 500 saw the bulk of their gains during the first two weeks of the month, though they managed to gain ground all through November. In fact, the only downturn came when the Nasdaq declined by 0.07% for the first week of the month.

A strong October jobs report from the Labor Department, a number of record highs for the Dow and S&P 500, and investors' focus on retailers as the holiday shopping season got under way during the Thanksgiving and Black Friday weekend were some of the key events that helped push stocks up in November.

Still, the blue-chip index managed to have four components finish the month lower than where they started. The worst performer was Cisco (NASDAQ:CSCO), down 5.8%, followed by AT&T, down 2.82%, Intel, down 1.97%, and Verizon, down 1.72%.

On the upside, the top-performing Dow component was Merck (NYSE:MRK), up 10.17%, followed by JPMorgan Chase, up 8.97% and UnitedHealthGroup, up 8.52% despite all the continued problems with the rollout of the Affordable Care Act and the online health care exchanges. But before we get into why Merck topped the list, let's take a moment to see why Cisco led the losers.

Cisco shares increased by 4.21% the first week of November and then fell the following three weeks, with the bulk of the decline coming during the second week. The company was the worst performer on the Dow that week, losing 8.37% following a quarterly earnings report in which the company beat Wall Street's expectations for earnings per share but missed on revenue. Cisco also reported that revenue for the fourth quarter would probably fall by 8% to 10% compared with the same quarter in 2012. As Cisco found out, when revenue begins to contract, investors go crazy and stocks tumble.

The month's big winner, Merck, gained a minimum of 1.81% each week. Its best performance was a 3.47% gain in the first week of November, good enough to make it that week's third best performing Dow component. Although Merck reported its Q3 results on Oct. 28, its full Form 10-Q came out on Nov. 7, allowing investors to dig deep into the numbers. They liked what they saw, because the bulk of Merck's gain for that week came the next day. and really find out what is going on with the company.

It's worth noting that Merck reported that sales had fallen to $11.03 billion from $11.48 in the previous year's Q3 -- but figuring out why it happened was nearly impossible until the full 10-Q came out. This is a good reminder that when earnings season rolls around, investors shouldn't trade based on headline news the day a company announces. Waiting for the 10-Q or 10-K report will give you a much fuller picture.

Fool contributor Matt Thalman owns shares of JPMorgan Chase. Check back Monday through Friday as Matt explains what caused the big winners and losers of the day, and every Saturday for a weekly recap. Follow Matt on Twitter: @mthalman5513

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