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Agenda
Efficient capital markets
Efficient market hypothesis
FINC341 Theory of Finance
Impossibility of perfectly efficient markets
Market efficiency and no arbitrage
Efficient Market Hypothesis
Lewis Tam
Motivations
1
Value of Information
One basic assumption of CAPM is that “all investors
analyze securities in the same way and share the same
economic view of the world. The result is identical
estimates of the probability distribution of future cash flows
from investing in the available securities.” (p.264, BKM)
The assumption implies an efficient market in which all
investors are rational, share the same set of information and
interpret the information in the same way.
We all know that such assumption is definitely wrong. But
how far does it deviate from the reality?
Lewis Tam
FINC341 Theory of Finance
FINC341 Theory of Finance
2
Information is relevant (or valuable) only when
1.
2.
it changes the distribution of possible outcomes; and
it changes your optimal course of action as a result of
the change in the distribution of possible outcomes.
Information => more precise forecast => better
decision making => higher utility
Value of information
= The expected utility with the information – the
expected utility without the information
Lewis Tam
FINC341 Theory of Finance
3
Reaction of Stock Price to New Information
in Efficient and Inefficient Markets
Efficient Capital Markets
Stock
Price
Efficient capital markets – the one in which stock
prices immediately and fully reflect available
information (efficient market hypothesis).
There are many investors out there doing research.
As new information comes to market, this information is
analyzed and trades are made based on this information.
Therefore, prices should reflect all available public
information.
Overreaction to “good
news” with reversion
Efficient market
response to “good news”
-30
Lewis Tam
FINC341...