FINS2624 Lecture Notes - Lecture 8: Efficient-Market Hypothesis, Abnormal Return, Fundamental Analysis
8 – EMH & Behavioural Finance
Market Efficiency
• Curret pries should reflet iestors epetatios aout future perforae
• If investors consider all currently available information when forming expectations,
only NEW information can move price
Could not have been inferred from currently available information – random
• Random Walks – market efficiency means stock prices follow random walk
Price changes randomly and independently of history
Only new information will move stock prices
New information is random and independent of history
Efficient Markets Hypothesis (EMH): States that market prices reflect available
information (fully or to some degree)
• Weak Form – reflects info from historical public trading data (price/volumes)
• Semi-Strong Form – reflects all public information about a firm
• Strong Form – reflects all available information about firm, even non-public
• Stronger forms of EMH imply weaker forms
• Requires fast & correct incorporation of relevant information into prices
• Info enters prices via investors looking to make profits through info advantage
Potential profit from information advantage is huge
Chance of discovering unknown information is small
Power of Crowds – errors in guesses wash out and average guess may be correct without
any individual being able to make accurate valuation
According to EMH, trading strategies based on current info should not be profitable
• Profitable strategy means to generate an abnormal return (non-zero alpha)
Technical analysis: Using patterns in past stock prices/returns/trading to predict future
returns
• If profitable, violates weak EMH
Fundamental analysis: Using publicly available data to uderstad opaies
fundamentals & to make superior valuations
• If profitable, violates semi-strong EMH
Insider trading (illegal): Using non-public information to gain informational advantage
• If profitable, violates strong EMH
Tests of EMH
• Hard to get sufficient statistical power since volatility of prices is large compared to
presumed effect of individuals or strategies beating market (too much noise)
• Risk of reporting bias – i.e. only studies with interesting information get published
• To beat market, need to control for priced risk (e.g. using CAPM)
Any test of EMH is test of validity of chosen pricing model
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Document Summary
Market efficiency: curre(cid:374)t pri(cid:272)es should refle(cid:272)t i(cid:374)(cid:448)estors(cid:859) e(cid:454)pe(cid:272)tatio(cid:374)s a(cid:271)out future perfor(cid:373)a(cid:374)(cid:272)e. If investors consider all currently available information when forming expectations, only new information can move price. Could not have been inferred from currently available information random: random walks market efficiency means stock prices follow random walk. Price changes randomly and independently of history. Only new information will move stock prices. New information is random and independent of history. Info enters prices via investors looking to make profits through info advantage. Potential profit from information advantage is huge. Chance of discovering unknown information is small. Power of crowds errors in guesses wash out and average guess may be correct without any individual being able to make accurate valuation. According to emh, trading strategies based on current info should not be profitable: profitable strategy means to generate an abnormal return (non-zero alpha) Technical analysis: using patterns in past stock prices/returns/trading to predict future returns.