Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.
So what: Neither of these numbers is what's worrying investors, though. What scared the pants off 'em were two others: Best Buy lost 110 basis points (that's "1.1%", to you and me) worth of its market share and saw its share price drop 15% in response.
Now what: According to management, rival retailers of flat-panel televisions and mobile computing devices stole customers during the Christmas sales season. Best Buy refused to enter into a price war with the competition, and fickle consumers opted to buy the same goods for lower prices, elsewhere. So you can probably blame Wal-Mart and Target, hhgregg and Costco for Best Buy's woes this week.
A more productive use of your time, however, might be to buy these Best Buy-rivals, on the assumption that Best Buy's loss must logically be their gain.
Will Best Buy join the price war? Will it win? Add Best Buy to your watchlist and find out.