Stocks for the Long Run? Sometimes yes. Sometimes no.

This academic paper challenges the long-held "Stocks for the Long Run" thesis popularized by Jeremy Siegel. By utilizing newly available digital archives, the author constructs a more comprehensive historical record of US stock and bond performance dating back to 1793, revealing that the 20th-century outperformance of stocks was not consistent with earlier periods. The analysis introduces a "regime perspective," suggesting that asset returns are subject to temporary patterns influenced by macroeconomic conditions rather than fixed, long-term relationships. International data further supports this view, demonstrating that in many markets and timeframes, bonds have outperformed stocks, and stock market downturns can be severe and prolonged. Ultimately, the paper argues that both stocks and bonds are risk assets, and historical performance, especially from the limited 20th-century lens, is not a reliable predictor of future returns.