Start of the business year, end of summer vacations, and back to school made September a leading barometer month in first 60 years of 20th century, now portfolio managers back after Labor Day tend to clean house. Since 1950, September has been the worst performing month of the year for DJIA, S&P 500, NASDAQ (since 1971), Russell 1000 and Russell 2000 (since 1979).
September was creamed four years straight from 1999-2002 after four solid years from 1995-1998 during the dot.com bubble madness. More recently, S&P 500 has been down in six of the last nine Septembers. September gets no respite from positive pre-election year forces.
Although the month used to open strong, S&P 500 has declined nine times in the last fifteen years on the first trading day. With fund managers tending to sell underperforming positions ahead of the end of the third quarter there have been some nasty selloffs near month-end over the years.
Recent substantial declines occurred following the terrorist attacks in 2001 (DJIA: –11.1%), 2002 (DJIA –12.4%), the collapse of Lehman Brothers in 2008 (DJIA: –6.0%), U.S. debt ceiling debacle in 2011 (DJIA –6.0%) and in 2022 (DJIA –8.8%).