Equity market seasonality refers to recurring patterns in stock market returns throughout the calendar year. Historical data on the S&P 500 from 1950 to 2024 shows that the November through April period has generated significantly higher average returns than the May through October period.
September stands out as the only month with a negative long-term average return, while February and August have been close to flat.
These seasonal trends are linked to structural factors such as tax cycles, capital flows, earnings visibility, and institutional portfolio rebalancing. However, outcomes vary widely year to year, and seasonality does not provide reliable short-term signals.
For portfolio construction, seasonality can be a useful reference point. It helps contextualize periods of stronger or weaker equity performance and supports discussions around diversification. Strategies outside public equities, including real assets and private markets, may behave differently and are not tied to the same seasonal cycle.