Mandelbrot and Hudson in
The (Mis) Behavior of the Markets dismiss the random walk as an explanation for market swings. The list of their ten heresies of finance:
- Markets are Turbulent
- Markets are Very, Very Risky
- Market Timing Matters Greatly
- Prices Often Leap, Not Glide
- In Markets, Time is Flexible
- Markets in All Places and Ages Work Alike
- Bubbles are Inevitable
- Markets are Deceptive
- You May be able to Estimate Future Volatility
- "Value" has Limited Value
Above all the Markets are not
normal! In other words they do not adhere to a bell shaped normal distribution of returns. This knocks all conventional wisdom on its head (CAPM, VAR, Black-Scholes, etc.)