CAPM and Market Efficiency

1. CAPM and Market Efficiency A summary

2. Individuals are greedy, form rational expectations, and maximize their expected utility.

3. Individuals are greedy, form rational expectations, and maximize their expected utility. We always produce the best estimates of cash flows, given the information available We care about E(R) and 

4. Individuals are greedy, form rational expectations, and maximize their expected utility. We always produce the best estimates of cash flows, given the information available We care about E(R) and  We hold only efficient portfolios, according to individual risk preferences. The efficient set is a curved line.

5. Individuals are greedy, form rational expectations, and maximize their expected utility. We always produce the best estimates of cash flows, given the information available We care about E(R) and  We hold only efficient portfolios, according to individual risk preferences. The efficient set is a curved line. Risk-free asset We hold a mix of cash and the (efficient) M. The efficient set is a straight line. M becomes the yardstick for risk.

6. Individuals are greedy, form rational expectations, and maximize their expected utility. We always produce the best estimates of cash flows, given the information available We care about E(R) and  We hold only efficient portfolios, according to individual risk preferences. The efficient set is a curved line. Risk-free asset We hold a mix of cash and the (efficient) M. The efficient set is a straight line. M becomes the yardstick for risk.  is a measures the relative risk. Risk premia per unit of relative risk is constant: (Ri - Rf)/ = RM - Rf

7. Individuals are greedy, form rational expectations, and maximize their expected utility. We always produce the best estimates of cash flows, given the information available We care about E(R) and  We hold only efficient portfolios, according to individual risk preferences. The efficient set is a curved line. We all use the same yardstick for risk to estimate stock prices: CAPM Risk-free asset We hold a mix of cash and the (efficient) M. The efficient set is a straight line. M becomes the yardstick for risk.  is a measures the relative risk. Risk premia per unit of relative risk is constant: (Ri - Rf)/ = RM - Rf

8. Individuals are greedy, form rational expectations, and maximize their expected utility. We always produce the best estimates of cash flows, given the information available We care about E(R) and  We hold only efficient portfolios, according to individual risk preferences. The efficient set is a curved line. We all use the same yardstick for risk to estimate stock prices: CAPM Risk-free asset We hold a mix of cash and the (efficient) M. The efficient set is a straight line. M becomes the yardstick for risk.  is a measures the relative risk. Risk premia per unit of relative risk is constant: (Ri - Rf)/ = RM - Rf

9. Individuals are greedy, form rational expectations, and maximize their expected utility. We always produce the best estimates of cash flows, given the information available We care about E(R) and  We hold only efficient portfolios, according to individual risk preferences. The efficient set is a curved line. We all use the same yardstick for risk to estimate stock prices: CAPM Risk-free asset We hold a mix of cash and the (efficient) M. The efficient set is a straight line. M becomes the yardstick for risk.  is a measures the relative risk. Risk premia per unit of relative risk is constant: (Ri - Rf)/ = RM - Rf

10. Individuals are greedy, form rational expectations, and maximize their expected utility. We always produce the best estimates of cash flows, given the information available We care about E(R) and  We hold only efficient portfolios, according to individual risk preferences. The efficient set is a curved line. We all use the same yardstick for risk to estimate stock prices: CAPM Risk-free asset We hold a mix of cash and the (efficient) M. The efficient set is a straight line. M becomes the yardstick for risk. Stock prices always represent the best estimation of future dividends and risk.  is a measures the relative risk. Risk premia per unit of relative risk is constant: (Ri - Rf)/ = RM - Rf

11. Market efficiency says that... There is no point in buying individual stocks, searching for bargains. They’re all correctly priced. Buy the market index and adjust your cash position for risk (borrowing & lending) Don’t delay that bond issue if interest rates are too high. They are never too high. Interest rates are always fair because they reflect future inflation and risk. It doesn’t matter if you issue bonds or stock. The market cares only about how you invest the money, not about how you raise money and distribute the results.

12. In other words... Stock prices move at random. There are no patterns in their movements. Although we produce the best estimates of stock prices (we know their probability distribution), we cannot forecast their movement from one period to another. Hence, we cannot beat the market. If we can’t beat it, we should join it. Buy the market portfolio. Buy and hold is as good as any other strategy

13. Market efficiency depends on: • The investment behavior of individuals • The availability of information

14. What if individuals are not rational? Overreaction and persistent stock price patterns. One can fool (the same) investors all the time.

15. What if information is not available to everyone? Different forms of market efficiency

16. Market Efficiency • Weak • Semi-strong • Strong

17. Why is market efficiency important? Market efficiency is needed to allocate resources to the most productive users