Capital Ideas — Chapter 6: Anticipating Prices Properly

1. 1. Paul Samuelson argued that most portfolio managers should go out of business because they cannot outperform a simple buy-and-hold strategy.
2. 2. Samuelson corrected Bachelier's assumption that security prices are as likely to go up as down, noting that prices cannot fall below zero due to limited liability.
3. 3. Samuelson's key insight was that the nonpredictability of future prices from past prices is a sign of the triumph of economic competition, not market failure.
4. 4. Samuelson introduced the concept of 'shadow prices' to represent intrinsic value, arguing that market prices are the best estimates of these unobservable true values.
5. 5. Samuelson's 'Proof That Properly Anticipated Prices Fluctuate Randomly' (1965) showed that if prices fully reflect all available information, they will move unpredictably.
6. 6. Samuelson stated that the expected excess return over the minimum required return is zero in speculative markets, meaning no easy pickings exist.
7. 7. Samuelson distinguished between individual stock predictability and aggregate market predictability, noting that bubbles can affect entire markets.
8. 8. Fischer Black argued that 'noise'—trading on rumors or misinformation—makes markets imperfect but also provides liquidity and motivation for informed traders.
9. 9. Black suggested that inside information, if acted upon, can actually drive prices toward intrinsic values, challenging the rationale for insider trading bans.