Pabrai gave this magmun opus talk, summarizing Buffett's last 70yrs.
In nutshell, most of Buffett's returns are coming from 11 companies and 1 person (Ajit).
And selection / future performance was a random event. It cant be predicted, just guessed with conservative assessment, folded hands, being in the market for long and random luck.
Graham also got his lion's share from GEICO investment.
Same, with Nick Sleep - most from amazon investment.
One company, held very very long, and hopefully successful, changes the course of returns.
--The End --
