Market efficiency Kevin C H Chiang Efficient market

Efficient market l (Informationally) efficient market: a market in which security prices adjust fully

3 sufficient conditions for an efficient market (Fama) l l l A large number

3 forms of market efficiency, I l Weak form: prices reflect all information contained

3 forms of market efficiency, II l Semi-strong form: prices reflect all publicly available

3 forms of market efficiency, III l Strong form: prices reflect all relevant information,

Testing l l l Does a known strategy produce consistently abnormal returns after adjusting

Implications, I l l In an efficient market, technical analysis is useless. In a

Implications, II l l In a semi-strong form efficient market, fundamental analysis is useless.

Passive management l l l No attempt to find undervalued securities. No attempt to

Active management/selection l l l Believe that one can beat the market. Find undervalued

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Market efficiency Kevin C. H. Chiang

Efficient market l (Informationally) efficient market: a market in which security prices adjust fully and rapidly to the arrival of new information and, therefore, the current prices of securities fully reflect all available information about the security.

3 sufficient conditions for an efficient market (Fama) l l l A large number of competing profitmaximizing participants analyze and value securities, each “independent” of the others. New information comes in a “random” fashion. The competing investors attempt to adjust security prices rapidly to reflect the effect of new information.

3 forms of market efficiency, I l Weak form: prices reflect all information contained in the history of past trading. Question: do past returns and prices predict future returns?

3 forms of market efficiency, II l Semi-strong form: prices reflect all publicly available information (earnings, dividends, PE ratios, book-to-market ratios, political news, etc. ) Question: how quickly do prices reflect all public information?

3 forms of market efficiency, III l Strong form: prices reflect all relevant information, including inside information. Question: Do insiders make abnormal returns?

Testing l l l Does a known strategy produce consistently abnormal returns after adjusting for investment risk and transaction costs? No: the market is quite efficient. Yes: evidence against the EMH.

Implications, I l l In an efficient market, technical analysis is useless. In a semi-strong form efficient market, fundamental analysts (country analysts, industry analysts, and company analysts), on average, will not outperform the market.

Implications, II l l In a semi-strong form efficient market, fundamental analysis is useless. In this market, a portfolio manager should: (1) determine a proper level of risk tolerance, (2) form a portfolio consisting of the risk-free asset and a well-diversified risky portfolio (passive management), and (3) minimize taxes and total transaction costs.

Passive management l l l No attempt to find undervalued securities. No attempt to time. Hold a well-diversified portfolio.

Active management/selection l l l Believe that one can beat the market. Find undervalued securities. Time the market.