Since 1928, U.S. stocks have massively outperformed bonds 
Total real return for a hypothetical $100 invested for each of the seventy 20-year spans between 1928-47 and 1997-2016. Investments in the U.S. stock market (S&P 500) are in red, investments in short-term U.S. treasury bills are in blue. Best, worst, and average performances are highlighted for each investment class. 
 
Source: returns data from Aswath Damodaran, inflation data from Robert Shiller