September historically marks the only month with a negative average return for the SPDR S&P 500 ETF since 2010, with an average loss of 0.48%. In contrast, October ranks as the third-best month for the fund, averaging a 2.27% gain. Despite this seasonal trend, the index faces internal weakness as 75% of its constituent stocks closed September lower.
Market breadth has reached its lowest level since May 2025. Currently, only 40.55% of S&P 500 stocks trade above their 200-day moving average, a decline of 2.59 points on September 30 alone. This metric has dropped approximately 32 points from its August peak of nearly 73%, falling below the April 2026 low of about 42%.
Sector performance in September was uneven, with banks like JPMorgan, Bank of America, and Wells Fargo, as well as software companies such as Salesforce, Adobe, and Oracle, experiencing declines. Conversely, technology firms including Micron, Apple, and Dell, along with GE Vernova and Eli Lilly, posted gains, sustaining the index despite broad market retreat.
While historical data shows recoveries following weak Septembers, such as in 2011, 2021, and 2022, recent trends are inconsistent. Three of the last six Octobers ended with losses. As of the start of October, the SPDR S&P 500 ETF maintains a year-to-date gain of 13.37%, though future stability may depend on broader participation across the index.
