Diversification is your buddy.

Everybody has some information. The function of the markets is to aggregate that information, evaluate it and get it incorporated into prices.

... Any pension fund manager who doesn't have the vast majority-and I mean 70% or 80% of his or her portfolio-in passive investments is guilty of malfeasance, nonfeasance or some other kind of bad feasance!

Most people might just as well buy a share of the whole market, which pools all the information, than delude themselves into thinking they know something the market doesn't.