| Month | Average Return | % Positive | Data Points |
|---|
Annual month-by-month returns for the S&P 500.
Historically, November and December are among the best months for the stock market, often driven by the "Santa Claus Rally" and strong Q4 institutional buying. April also shows consistently strong average returns.
September is historically the worst month for the S&P 500. This phenomenon is known as the "September Effect," where average returns are often negative as institutional investors return from summer vacations and reposition portfolios.
It is an investment adage suggesting that the stock market underperforms during the six-month period from May to October compared to the November to April period. Investors are historically advised to sell stocks in May and buy them back in November.
The January Effect is a seasonal increase in stock prices during the month of January. It is often attributed to tax-loss harvesting in December followed by repurchasing in January, as well as the deployment of year-end bonuses.
While historical data shows clear seasonal trends (like the September Effect), these are averages over many decades. In any given year, macroeconomic factors, interest rates, and earnings heavily outweigh seasonal patterns, meaning seasonality should not be the sole basis for investing decisions.
This study analyzes historical S&P 500 (Ticker: ^GSPC) adjusted closing price data from 1950-2026. Data is sourced directly via the Yahoo Finance API.
Monthly returns are calculated as the percentage change in the adjusted close price from the end of the previous month to the end of the current month. The adjusted close accounts for corporate actions like stock splits and dividends (total return).
Note: Past performance is not indicative of future results. Seasonal patterns represent statistical averages, and individual years may vary significantly from these historical norms.
Westmount Fundamentals. "S&P 500 Returns by Month." westmountfundamentals.com/sp500-returns-by-month, 2026.