Key Takeaways
- Historical data shows September delivers the poorest performance for major U.S. equity indexes including the S&P 500, Dow Jones, and Nasdaq
- Both the S&P 500 and Dow Jones typically fall 1.1% during September, with success rates under 45%
- Market participants are focused on the Federal Reserve’s September 16 policy announcement following a surge in rate hike probability from 35% to 60%
- Portfolio rebalancing by institutional investors returning from August vacations historically contributes to downward pressure
- Historical analysis reveals that avoiding September trading typically diminishes long-term gains and creates unfavorable tax consequences
Wall Street veterans know September wellāand for good reason. Historical performance data from Dow Jones Market Data confirms that the ninth month consistently delivers the weakest average returns across the S&P 500, Dow Jones Industrial Average, and Nasdaq Composite.
Data reveals that both the S&P 500 and Dow Jones have declined by an average of 1.1% during September. The S&P 500 has finished September in positive territory just 44.5% of the time throughout its history. The Dow’s success rate is even more dismal at 42.6%.
The Nasdaq shows marginally better performance, posting gains in 52.7% of September periods since its 1971 inception. However, the technology-heavy index still averages a 0.8% decline for the month.
Understanding September’s Market Headwinds
No single explanation accounts for this persistent seasonal weakness. Market analysts point to institutional portfolio managers returning from August holidays and adjusting their holdings. Tax-loss harvesting strategies often drive these professionals to liquidate losing positions before the calendar year concludes.
The Federal Reserve’s mid-month policy meeting represents another significant factor. Widespread media attention surrounding the “September Effect” can trigger preemptive selling in late August, creating downward momentum that extends into early September.
Arnim Holzer, who serves as global macro strategist at Easterly EAB, characterizes September as a “historically less forgiving period” for stock market participants.
Market participants are particularly focused on the Fed’s September 16 gathering this year. Following Fed Chair Kevin Warsh’s Jackson Hole remarks emphasizing continued inflation control efforts, rate hike expectations surged from 35% to 60% based on CME FedWatch Tool data.
Government bond yields have been advancing steadily. The benchmark 10-year Treasury yield has climbed from 4.2% to 4.7% year-to-date.
Peter Boockvar of One Point BFG Wealth Partners suggests the fixed income market may currently hold more significance than Federal Reserve policy. He argues that the yield curve has already incorporated higher capital costs, while inflation metrics have constrained the central bank’s policy flexibility.
The Case for Staying Invested
Ryan Detrick, who holds the position of chief market strategist at Carson Group, observes that historically severe September declines occurred during periods of existing market weakness or elevated uncertainty. He believes current conditions don’t match that description.
The S&P 500 advanced approximately 3% during August, and Detrick highlights that across 11 comparable scenarios since World War II, September delivered negative returns only once.
Melissa Browne of SimCorp offers a note of caution, suggesting that robust August performance can prove difficult to sustain, particularly during quiet earnings periods with elevated interest rates.
Historical analysis suggests investors contemplating a September exit should reconsider. Data indicates that systematically avoiding September since 2021 would have generated a 136% return compared to 124% for continuous investors, yet capital gains tax obligations would eliminate most of that apparent advantage.
Critical economic releases arrive during early September. The ISM Manufacturing PMI is scheduled for September 1, followed by the employment situation report on September 4, and the August consumer price index on September 11.
July’s employment report revealed a 23,000 job decline, intensifying focus on August’s labor market data.
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