September Almanac: Bearish Bias Last 75 Years By: Jeffrey A. Hirsch & Christopher Mistal | August 21, 2025 | Email | Print

Portfolio managers back after Labor Day have tended to clean house in September. 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 madness. More recently, DJIA, S&P 500, NASDAQ, Russell 1000 and 2000 have been down seven of the last eleven Septembers and four of the last five. Average losses over the last eleven years range from –1.2% by DJIA to –2.4% from NASDAQ and Russell 2000.

 

In post-election years, September’s overall rank improves modestly in post-election years going back to 1953 (third or fourth worst month depending on index). Average losses are little changed. Although September 2001 does influence the average declines, the fact remains DJIA and S&P 500 have declined in 10 of the last 18 post-election year Septembers. Russell 2000 has the best post-election year record, up seven times in 11 post-election years.

 

 

Although the S&P 500 has advanced 18 times over the last 30 years on September’s first trading day, strength has faded more recently with average performance over the last 21 years turning negative. 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 full-month 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 during the post-covid bear market in 2022 (DJIA –8.8%).

 

 

September Triple Witching week has been generally bullish with S&P 500 advancing three times for every two declines since 1990, but it has suffered some sizable losses, and weekly performance has deteriorated noticeably since 2018 with NASDAQ declining in six of the last seven. Triple-Witching Friday was essentially a sure bet for the bulls from 2004 to 2011 but has been a loser nine, ten, or eleven of the last thirteen years, depending on index with S&P 500 weakest, down 12 of the last 13. The week after Triple Witching has been brutal, S&P 500 down 27 of the last 35, averaging a loss of 1.05%. In 2022, DJIA, S&P 500, and NASDAQ all dropped 4% or more.

 

Labor Day has become the unofficial end of summer, and the three-day weekend is prime vacation time for many. Business activity ahead of the holiday was more energetic in the old days. From 1950 through 1977 the three days before Labor Day pushed the DJIA higher in twenty-five of twenty-eight years. Bullishness has since shifted to favor the Wednesday after the holiday as opposed to the days before. DJIA has advanced on 22 of the last 30 Wednesdays following Labor Day. Tuesday after Labor Day also leaned bullish, but DJIA has declined 12 of the last 15 (down the last 8 straight).