In 2006, Warren Buffett bet a million dollars that the most brainless, boring investment around would do better than the researched, handpicked investments of some of the smartest hedge fund managers in the world. The second class of Summer School looks at how that bet played out, the origins of the index fund, and why it's so hard to beat the market. Returning to the underlying theme of risk and reward, we also discuss how diversification reduces risk.