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 stock market's remarkable rally, nearly five years in the making now, is becoming harder and harder to ignore. The Dow Jones Industrial Average (DJINDICES:^DJI), which closed at a mere 6,507 on March 9, 2009, has roared back with a vengeance, surging almost 10,000 points since that bleak winter day in the depths of the recession. Today would have been impossible to imagine in the early winter months of 2009: The stock market fell because of concerns the economy is doing too well. Stoked by fears that an improving economy spells Federal Reserve tapering, the Dow fell 77 points, or 0.5%, to end at 16,008. 

The Institute for Supply Management's November manufacturing survey posted the strongest reading in more than two and a half years, giving the Fed one more reason to begin tapering its $85 billion-a-month quantitative easing efforts. Such a move would be booed loudly by Home Depot (NYSE:HD) investors, a risk that evidenced itself in the stock's 1.1% drop today. The reliable ol' Fed stimulus has kept interest rates at rock-bottom levels, fueling the real estate market and with it the remodeling industry, Home Depot's bread and butter. 

Sears Holdings (OTC:SHLDQ), on the other hand, saw shares falling for a less speculative reason: an unimpressive sales environment. Shares of the retailer, which not only owns its namesake line of department stores but also the big-box retailer Kmart, fell 5.2% today after numbers from the National Retail Federation revealed consumers didn't splurge like they did last year. Aggressive holiday pricing probably contributed to the $407 tab of the average shopper this year, down $15 from last year. Sears Holdings, which has considered selling its successful Lands' End brand to raise capital, would prefer to see more impulsive, less savvy consumers this holiday season.

Lastly, Myriad Genetics (NASDAQ:MYGN) stock slumped 9.3% Monday, as the maker of genetic diagnostics came under fire from a rival. Today's sell-off wasn't just the result of standard competitive bickering, either -- Myriad Genetics is being sued by an opponent, Invitae. Investors should be used to this sort of controversy by now, however, as Myriad's line of business is to lawsuits what honey is to bees. The company makes tests screening for signs of breast cancer, and intellectual property involving genetics is a gray area in patent-land -- a very expensive gray area for Myriad shareholders. It also appears that the government may be reimbursing those who use Mryiad's breast cancer product at a lower rate than investors expected, which would boost the effective cost of the product for consumers.