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 ended a phenomenal week on a strong note, with major indexes trading higher into the last weekend before Christmas. A vote of confidence in the U.S. economy from the Federal Reserve earlier this week was followed by today's revision to third-quarter GDP numbers out of the Commerce Department. Third-quarter GDP growth had previously been estimated at 3.6%, but it turns out higher-than expected consumer spending puts that number closer to 4.1%. The S&P 500 Index (^GSPC 0.17%) applauded the data, added eight points, or 0.5%, to end at another all-time closing high, 1,818. 

Peabody Energy (BTU) stock fell 4.7%, ending as one of the index's worst decliners despite the broader market's bullishness. Project stoppages and labor disputes have put a damper on results from operations this year, the company said yesterday. Peabody Energy lowered its estimates for earnings before interest, taxes, depreciation, and amortization, or EBITDA, for fiscal 2013 by $60 million-$80 million from the $1.07 billion to $1.15 billion level it previously expected. 

Best Buy (BBY -1.42%) stock lost 4.1%, ending as the sole retailer on today's shortlist of laggards. A 4% stumble isn't so bad in the context of this year's 230% rally to recent highs. Best Buy has proven it's still able to compete with the big boys, and with a few days to go before Christmas, retailers are still hoping to attract last-minute shoppers with steep discounts. This competitive, promotion-driven environment, however, is keeping margins at a minimum as we approach some of the busiest shopping days of the year.

Lastly, shares of Cliffs Natural Resources (CLF 0.47%) shed 2.7%. Like Peabody, Cliffs Natural Resources is a coal miner, though it also produces iron ore. Last week, the company reached a six-year labor agreement with the United Steelworkers Union, which should bring some lasting stability to the company's labor relations. Cliffs has smartly positioned itself as a diversified materials company that markets two of the key ingredients in steel, which recently has served as a hedge for shareholders: since May, for instance, the price of iron ore is up more than 20% while coking coal is down 4%. As long as demand from China keeps up, Cliffs Natural should keep plenty busy.