Historical data show December remains the strongest month for U.S. stocks, with the S&P 500 rising in 73.2% of Decembers since 1928, the highest win rate of any month. Over the past 97 years, the index posted a negative December return in only 26 instances.
Across that full period, the S&P 500 delivered an average December gain of 1.28%, reinforcing the month’s reputation as a seasonally favorable window for equities. From 1945 onward, average December performance improves further, reaching about 1.50% as postwar market structure and institutional participation deepened.
Strategists often link this pattern to year-end positioning, tax planning, and improved risk sentiment, though they stress that historical seasonality does not guarantee future gains. Even so, December’s track record remains a key reference point for investors assessing equity exposure into the close of the calendar year.