What Long-Term S&P 500 Data Show About Returns and Risk

Long-term S&P 500 data provide several ways to assess past market performance without relying on unsupported probability estimates.

Nasdaq Dorsey Wright analyzed S&P 500 total returns beginning in 1950 across multiple investment horizons. Its analysis found a positive S&P 500 return in 97% of historical 10-year periods. Over 20-year periods, the analysis found that an investment at least doubled in every historical period it examined.

S&P Dow Jones Indices reported an annualized 20-year total return of 11.00% for the S&P 500 through December 31, 2025. The index’s annualized 20-year volatility over the same period was 15.09%, according to the same source.

Together, the figures describe the index from different angles: Nasdaq Dorsey Wright’s results focus on historical outcomes across holding periods, while S&P Dow Jones Indices provides return and volatility figures for a 20-year period ending in 2025. Neither source establishes how the S&P 500 will perform in the future.

The data therefore support a measured conclusion: the S&P 500 has produced generally favorable long-term historical results in the cited analyses, while its performance has also included volatility.