An old joke poking fun at the efficient market theory has an economist walking down the street and noticing a $20 bill on the pavement. “Why don’t you pick it up?” his walking partner asks, to which the efficient market theorist responds, “It can’t be there; if it really were, someone would have picked it up already.”
Actually, the analogy that makes the joke funny is flawed. The efficient market theory doesn’t say that bargain-priced securities don’t exist, just that the bargains are so rare and so fleeting that basing an investment strategy on them doesn’t make sense.