US stock market indexes fell Monday, trimming their gains for the month.
The Dow Jones Industrial Average lost nearly 48 points, or 0.5 percent of its value, to close at 9496. The Standard & Poor's 500 Index lost 0.8 percent to close at 1020. The Nasdaq lost nearly 1 percent of its value, closing at 2009 points.
What that means is that the S&P 500 finished August with its second-weakest monthly rise since the markets began rebounding in March and now enters the notoriously treacherous month of September.
Historically, investors have fared worse in September than in any other other month of the year. Since 1929, the S&P 500 has declined 56 percent of the time and lost an average 1.3 percent in that month.
Last September, the bankruptcy of Lehman Brothers dragged down the S&P 9.2 percent for the month – nearly a quarter of the index's entire loss for the year.
Another reason for caution is technical. The Federal Reserve, which was actively pumping money into the economy through 2008, abruptly stopped in 2009. It usually takes eight months for the end of the pump-priming to depress the stock markets, Tom McClellan, a well-known technical analyst and editor the McClellan Market Report, pointed out in a recent interview.
Still, the month's historical record isn't all bleak, points out Sam Stovall, chief investment strategist for Standard & Poor's Equity Research, writes in an analysis. Since 1932, the Septembers following the end of bear markets have risen a median 2.0 percent.