September notoriously often leaves markets in negative territory. Since the start of the Dow Jones Industrial Average in 1896, the index has lost an average of 1.07% in September, with a 0.71% average gain for all other months.
That's a 1.78-point spread - enough to be "statistically significant at the 95% confidence level," and be considered a genuine pattern by statisticians.
More discouraging, the market has performed especially poorly in past Septembers when the preceding months were weak.
And that's where we are today.
August took markets on a wild ride. The Standard & Poor's 500 Index fell 5.7% and the Dow 4.4%. The month included two of the top ten worst-performing Dow days ever - a 635-point drop on Aug. 8 and a 513-point drop on Aug. 4.
Now with investors digesting a slew of disappointing economic reports, and the U.S. Federal Reserve unlikely to announce any stimulus measures until the end of the month at the earliest, it doesn't look like this September will buck the trend.
In fact, it could easily be worse.