From LA Times:
Stock investors hoping for a bit of relief after a rough August, take warning: September is historically a bad month for stocks, and this one offers a few more potholes than usual.
September is the only month of the year in which the Standard & Poor’s 500 index has fallen more often than it has risen in the post-World War II era, according to Sam Stovall, U.S. equity strategist for S&P Capital IQ. It’s also the month that has produced the worst average return, a negative 0.63%, compared with a positive 0.66% for the average month from the end of 1945 through Friday.