Quick Overview
- Wall Street’s calendar shows September as the weakest performing month for major U.S. stock indices
- Both the S&P 500 and Dow Jones typically fall 1.1% during September, with success rates under 45%
- Markets are focused on the Fed’s September 16 policy meeting as rate hike probability surged from 35% to 60%
- Portfolio rebalancing by returning fund managers typically adds selling pressure during this period
- Historical data shows investors who avoid September entirely sacrifice long-term gains and face higher tax liabilities
Wall Street traders know September’s reputation all too well, and historical data confirms their concerns. Major U.S. equity benchmarks including the S&P 500, Dow Jones Industrial Average, and Nasdaq Composite consistently deliver their poorest average performance during this month, data from Dow Jones Market Data reveals.
Both the S&P 500 and Dow Jones record average declines of 1.1% throughout September. The S&P 500’s track record shows gains in just 44.5% of all Septembers historically. The Dow’s success rate trails even further at 42.6%.
While the Nasdaq demonstrates marginally better performance with positive returns in 52.7% of Septembers since its 1971 inception, the tech-heavy index still averages a 0.8% loss during this month.
The Forces Behind September’s Market Weakness
Multiple factors contribute to this seasonal pattern rather than a single catalyst. Portfolio managers commonly return from August holidays and adjust their holdings during September. Many choose to realize losses on underperforming positions for tax-loss harvesting strategies ahead of the calendar year’s end.
The timing of the Federal Reserve’s mid-month policy announcement adds another layer of uncertainty. Widespread media attention surrounding the “September Effect” phenomenon can trigger preemptive selling in late August, creating momentum that carries into the following month.
Arnim Holzer, who serves as global macro strategist at Easterly EAB, characterizes September as a “historically less forgiving period” for stock investors.
Market participants are particularly focused on the Fed’s September 16 policy announcement this year. Following Fed Chair Kevin Warsh’s remarks at the Jackson Hole symposium emphasizing continued inflation reduction efforts, market-implied probability of a rate increase surged from 35% to 60%, based on CME FedWatch Tool data.
Government bond yields have shown steady upward movement as well. The benchmark 10-year Treasury yield has advanced from 4.2% to 4.7% year-to-date.
Peter Boockvar from One Point BFG Wealth Partners suggests the bond market’s signals may carry more weight than Federal Reserve actions currently. He argues that the yield curve has already incorporated expectations for elevated capital costs, while inflation readings have constrained the central bank’s policy flexibility.
Should Buy-and-Hold Investors Stay the Course?
Ryan Detrick, who holds the position of chief market strategist at Carson Group, observes that September’s most severe declines occurred during periods of existing market weakness or heightened uncertainty. Current conditions don’t match that description, he argues.
Following the S&P 500’s approximately 3% August advance, Detrick highlights that among 11 comparable scenarios since World War II’s conclusion, September delivered negative returns only a single time.
However, Melissa Browne from SimCorp warns that maintaining momentum after strong August performance proves challenging, particularly during quiet earnings periods with interest rates remaining elevated.
Investors contemplating a September hiatus face unfavorable mathematics. Analysis indicates that systematically avoiding September since 2021 would have generated 136% returns compared to 124% for consistent investors, yet short-term capital gains taxation would eliminate the majority of that outperformance.
Critical economic releases arrive during September’s opening days. The ISM Manufacturing PMI publishes September 1, followed by employment data on September 4, with the August consumer price index arriving September 11.
July’s employment report revealed a 23,000 job decline, elevating scrutiny on the forthcoming August figures.
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