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Explore how Efficient Market Hypothesis impacts business, investment, and finance. Learn about Random Walk theory, types of EMH, stock analysis, active vs. passive management, and empirical tests on market efficiency. Discover anomalies in security prices and mutual fund performance evaluation.
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Chapter9 The Efficient Market Hypothesis
Efficient Market Hypothesis (EMH) • Do security prices reflect information ? • Why look at market efficiency • Implications for business and corporate finance • Implications for investment
Random Walk and the EMH • Random Walk - stock prices are random • Actually submartingale • Expected price is positive over time • Positive trend and random about the trend
Random Walk with Positive Trend Security Prices Time
Random Price Changes • Why are price changes random? • Prices react to information • Flow of information is random • Therefore, price changes are random
EMH and Competition • Stock prices fully and accurately reflect publicly available information • Once information becomes available, market participants analyze it • Competition assures prices reflect information
Forms of the EMH • Weak • Semi-strong • Strong
Types of Stock Analysis • Technical Analysis - using prices and volume information to predict future prices • Weak form efficiency & technical analysis • Fundamental Analysis - using economic and accounting information to predict stock prices • Semi strong form efficiency & fundamental analysis
Implications of Efficiency for Active or Passive Management • Active Management • Security analysis • Timing • Passive Management • Buy and Hold • Index Funds
Market Efficiency and Portfolio Management Even if the market is efficient a role exists for portfolio management • Appropriate risk level • Tax considerations • Other considerations
Empirical Tests of Market Efficiency • Event studies • Assessing performance of professional managers • Testing some trading rule
How Tests Are Structured 1. Examine prices and returns over time
Returns Surrounding the Event -t 0 +t Announcement Date
How Tests Are Structured (cont.) 2. Returns are adjusted to determine if they are abnormal Market Model approach a. Rt = at + btRmt + et (Expected Return) b. Excess Return = (Actual - Expected) et = Actual - (at + btRmt)
How Tests Are Structured (cont.) 2. Returns are adjusted to determine if they are abnormal Market Model approach c. Cumulate the excess returns over time: -t 0 +t
Issues in Examining the Results • Magnitude Issue • Selection Bias Issue • Lucky Event Issue • Possible Model Misspecification
What Does the Evidence Show? • Technical Analysis • Fundamental Analysis • Anomalies Exist
Anomalies • Small Firm Effect (January Effect) • Neglected Firm • Market to Book Ratios • Reversals • Value Line Enigma • Post-Earnings Announcement Drift • Higher Level Correlation in Security Prices
Mutual Fund and Professional Manager Performance • Some evidence of persistent positive and negative performance • Potential measurement error for benchmark returns • Style changes • May be risk premiums • Superstar phenomenon