Today’s Chart of the Day comes from S&P Dow Jones, which just celebrated 20 years of tracking market metrics, and shows only 18% of stocks outperformed the average during that time. One reason why is that many companies don’t last 20 years; a recent study by McKinsey showed that the average lifespan of companies on the S&P 500 went from 61 years in 1958 to only 18 years today. Many are bought out, merged, or become bankrupt.