> it's not unheard of to value an S&P index fund at 10% over that period! It's also not unheard of for shares to double in value over a short period, but you d

> it's not unheard of to value an S&P index fund at 10% over that period! It's also not unheard of for shares to double in value over a short period, but you don't know in advance which ones. Quite simply, you are very unlikely to average at least 10% p.a. above inflation on investments over a long period.