Buffett did something that finance theory says no investor should be able to do: He beat the market, consistently, by huge amounts. (..) A likelier explanation is that in the 1960s, 1970s, and 1980s, the U.S. stock market was just somewhat inefficient — investors were just making a bunch of dumb bets. (..) Eventually, as more investors learned to be cool and rational like Buffett, his advantage over the market decreased. ^^ Noah Smith re Warren Buffet