I think you missed my point. If he had a large lump sum and invested in 1929 and never invested another thing, he would have made exactly nothing by 1950. Okay, I'll take your stats as given. My point is, that if he doesn't let himself get frightened out of the market and continues to invest in 1930, 31, 32 etc., then he will make money with his investments even though the investment he made in 1929 did terribly, looked at in isolation. I'm trying to talk up the merits of disciplined investing, rather than market timing which is far more often than not a losing strategy.

And you stopped in 1950, not 1969, when our hypothetical 25-year-old would actually retire. What really matters is how you did at the end of the race, not in any one stretch.