We source real inflation from ShadowStats.com. This measure keeps the methodology the same since 1980 and dispenses with all those great ways of obfuscation of the real thing. Then we take series of multiplication to get the compounded rate of inflation since 1990 to target year. Next is reading of monthly chart of SPX the dollar value of investment plus multiplication with compounded inflation and there you go.
Isn’t it interesting? Is there purchasing power heaven?