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.

Strong manufacturing data from both the U.S. and global industrial leader China impressed Wall Street on Friday, sending the stock market higher. The gains nearly erased yesterday's losses, which were sparked by declining consumer confidence and underwhelming jobless claims numbers from last week. The S&P 500 Index (SNPINDEX:^SPX) added 5 points, or 0.3%, to end at 1,761. Despite the bullish start to November, a majority of stocks actually fell today, so today's three biggest S&P decliners were in good company. 

Insurance giant American International Group (NYSE:AIG) slumped 6.5% after reporting its third-quarter earnings. Although profits jumped 17%, in line with estimates, a few important caveats drove shares lower. For one, AIG didn't even turn a profit on its property and casualty business: It paid out more claims than it earned in premiums for the quarter. Also, the Wall Street research group Sterne Agee maintained its neutral rating on AIG stock, lamenting that the company only met expectations due to unique onetime accounting issues.

Biotech Vertex Pharmaceuticals (NASDAQ:VRTX) fell 5.6% as fallout continued to hit the stock after the company's third-quarter results. Vertex announced earlier this week that it would have to cut 15% of its workforce after sales of its cash cow, hepatitis C treatment Incivek, came in weaker than expected. Downbeat analyst commentary continues to trickle in, with Friday's pessimism coming from Bernstein, which downgraded the stock to market perform from outperform, citing valuation, volatility, and uncertainty surrounding the company's current trials for its cystic fibrosis treatment.

Lastly, gold and copper miner Newmont Mining (NYSE:NEM) dropped 4.7%, also on the heels of a Wall Street downgrade. This was of a different ilk, however, as S&P Rating Services downgraded Newmont Mining's credit rating rather than its stock. The rating agency thinks that the falling price of gold hurts its ability to pay back creditors, bestowing it with a BBB rating, down from BBB+. The company also announced third-quarter results, where it blew past analyst profit expectations. But with sales still down 20% year over year and the price of gold down yet again on Friday, shares didn't stand much of a chance heading into the weekend.