Looking For Black Swans In September

September has just started, and it is already living up to its reputation of being the toughest month of the year for stock prices which tumbled today during the first trading day of the month. So did commodity prices, led downward by oil and copper. The stock market selloff started when it opened and before August's weak M-PMI report was released at 10:00 a.m. EST, which put more downward pressure on stock prices. Leading the way down in the S&P 500 were the semiconductor stocks, which have been especially volatile lately.

That's a bummer given that just yesterday, we wondered out loud what could possibly go wrong? We didn't have a good answer. One account responded to our analysis by observing that he worries most when there doesn't seem to be much to worry about.