[astrange]

The S&P 500 just didn't exist before 1957, so it can't say anything about back then. Remember S&P 500 is actually a specific (actively-managed!) large cap index.

I'm not sure what the return on all US stocks is since then, but Japan's market has only just returned to the level it was at in its 80s bubble.

[llampx]

Right, there was an index in place during the Great Depression for sure. From wikipedia: https://en.wikipedia.org/wiki/S%26P_500

History

In 1860, Henry Varnum Poor formed Poor's Publishing, which published an investor's guide to the railroad industry.[20]

In 1923, Standard Statistics Company (founded in 1906 as the Standard Statistics Bureau) began rating mortgage bonds[20] and developed its first stock market index consisting of the stocks of 233 U.S. companies, computed weekly.[1]

In 1926, it developed a 90-stock index, computed daily.[1]

In 1941, Poor's Publishing merged with Standard Statistics Company to form Standard & Poor's.[20][21]

On March 4, 1957, the index was expanded to its current 500 companies and was renamed the S&P 500 Stock Composite Index.[1]