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.

This week was tough for the S&P 500 Index (SNPINDEX:^GSPC), which posted its worst week of trading since August as investors braced for the possibility of a Federal Reserve taper going into effect next week. Not only is the much-anticipated December Fed meeting going down next week, but the Senate will vote on the 2014 and 2015 budget that just passed in the House today. Janet Yellen is also expected to be formally approved as Fed Chairman Ben Bernanke's successor. Today, the S&P 500 ended the lackluster week by falling 0.2 points, or less than 0.1%, to end at 1,775. 

Oil and natural gas explorer Anadarko Petroleum (NYSE:APC) was by far the worst performer in the 500-stock index, with shares slumping 6.4%. A major legal ruling went against Anadarko Petroleum today as a judge ruled the company would be responsible for between $5.2 billion and $14.2 billion in liabilities incurred by a spinoff of Kerr-McGee, a company Anadarko picked up in 2006. The ruling has less obvious negative repercussions on Anadarko's cost of capital, which could go up judging by Moody's decision to downgrade the outlook on the company's debt to "developing" from "positive."

Old-school payment processing service Western Union (NYSE:WU) saw its stock fall 1.6%. While the market for payment processing continues to grow, Western Union faces a ton of competitors, many of which are making a name for themselves in the world of the web. eBay's PayPal has been in the game for years, but Google and also have their own services, and even the up-and-coming bitcoin networks represents a long-term threat to industry dynamics. Western Union also went ex-dividend today, putting additional downward pressure on shares. 

Lastly, shares of Eastman Chemical (NYSE:EMN) were notable underperformers, falling 1.6% in trading. Strangely enough, the materials sector was the strongest part of the markets Friday, so Eastman Chemical's slide stood out like a sore thumb. Though there was no glaring reason for today's sell-off, the stock hasn't exactly been the darling of momentum-based investors, who've recoiled in disgust at Eastman's five-day losing streak. Needless to say, this is not the smartest way to think about investing, and the fact that Eastman's board approved a 17% dividend hike earlier this month is proof that the company remains in fine financial condition.