Will Last Week's Stock Sell-Off Trip Up the Bull Market?

Stocks tumbled over the past week - despite a sharp 3% drop in crude oil prices - as investors fretted about the devastating earthquake in Japan, a downgrade of Spain's sovereign debt rating, weak trade data out of China, Germany and the United States and violence in Saudi Arabia. The Dow Jones Industrial Average closed down by 1% for the week, while the Nasdaq Composite Index finished down 2.5% and the Russell 2000 small caps fell 2.7%. The stock sell-off was punctuated by a 90% downside day on Thursday, which means nine out of 10 stocks finished lower and 9/10 of the volume was in declining stocks. Selling was intense and there appeared to be what The Street calls "real money" selling, which means not just speculators but individuals and institutions. Measures of buying power retreated to its lowest level of the year, while selling pressure is at its highest. Defensive stocks were relatively strong, led by McDonalds Corp. (NYSE: MCD ) and Altria Group Inc. (NYSE: MO ) - burgers and cigarettes. So what does it all mean?