A lot of investors hold concentrated positions in individual stocks. This can happen when you hear Charlie Munger say that “diversification is for the know-nothing investor” without realizing that he’s talking about you, or for other reasons like being part of a company that went public and holding onto your stock, or owning stock in an employer that has performed so well that it becomes a large part of your portfolio. In any case, I don’t think people are aware of how risky individual stocks are.