No month has brought worse results in the stock market than September.
Here is the average monthly price change, from 1950 through July 2010, for the Standard & Poor's 500 index. Months are listed from best performance to worst:
December: 1.6 percent gain
November: 1.6 percent gain
April: 1.5 percent gain
March: 1.2 percent gain
January: 1 percent gain
July: 1 percent gain
October: 0.6 percent gain
May: 0.3 percent gain
August: 0.1 percent gain
June: 0.04 percent loss
February: 0.2 percent loss
September: 0.6 percent loss
— Source: Stock Trader's Almanac