Organizational learning and technology development
Presentation portfolio theory
1. Sharif University of Technology
Electrical Engineering Department
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Information-Theory And Portfolio Selection Strategies
Omid Aminzadeh Gohari
- Bsc.Project Presentation -
4th July 2010
2. Sharif University of Technology
Electrical Engineering Department
Agenda
Why should we care about the stock market?
Information Theory and the Stock Market
Many works
Chen’s approach
Cover&Thomas’s approach
Concepts and Terminology
A sample result
Conclusion
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Electrical Engineering Department
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Why should we care about the stock market
The “stock market” began in May 17th, 1792 when 24 stock brokers and
merchants signed the Buttonwood Agreement.
Financial Aspects
50% - A rough estimate of the rise in the share price of Apple in the aftermath of the
iPhone.
$36.6 trillion - the estimated size of the world stock market at the beginning of October
2008.
So, let’s start our own business
Caveat: Timing is everything!
McDonald's stock $22.5 in 1965 - was worth well over $14000 in
1995.
In 2003, they'd only be worth $25!!
Not everyone is a winner! Using information theory to understand the
market
4. Sharif University of Technology
Electrical Engineering Department
Agenda
Why should we care about the stock market?
Information Theory and the Stock Market
Many works
Chen’s approach
Cover&Thomas’s approach
Concepts and Terminology
A sample result
Conclusion
4
5. Sharif University of Technology
Electrical Engineering Department
Chen’s approach
M : number of persons in the market,
p: percentage of those who have a product (scarcity),
-log(p): financial value of the product per unit.
Total value of the product:
Mp(−log p)
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Electrical Engineering Department
Chen’s approach: information in a market
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Value of information Number of people who know
it
Low
High
High
Low
Free Information
Transmitter in a
communication
system
Receiver in a
communication
system
A broker
7. Sharif University of Technology
Electrical Engineering Department
Agenda
Why should we care about the stock market?
Information Theory and the Stock Market
Many works
Chen’s approach
Cover&Thomas’s approach
Concepts and Terminology
A sample result
Conclusion
7
8. Sharif University of Technology
Electrical Engineering Department
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The Stock Market
We can represent the stock market as a vector of stocks
1 2 ( , X X X ,..., Xm ), Xi 0, i 1, 2,...,m
m: Number of stocks
Xi: Price relatives, ratio of price of stock i at the end of the day to the
beginning.
x F(x): Joint distribution of the vector of price relatives
Price ratios are i.i.d over time
Portfolio: Allocation of wealth accross various stocks.
m
b b b b b i b
( , ,..., ), 0, and 1
1 2
m i i
where bi is the fraction of wealth allocated to stock i.
1
i
Example: Ali has wealth $100 and her portfolio consists of
the following fractions: 50% in IBM, 25% in Disney, 25% in
GM
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Electrical Engineering Department
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Concepts and Terminology
Wealth-Relative: Ratio of wealth at the end of the day to the
beginning of the day
We want to maximize S in some sense and find the optimal
portfolio!
T S = b X
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Electrical Engineering Department
T T T T
b X b X b X b X
log( ) log( ) log( ) ... log( )
(log( )) (log( )) (log( )) ... (log( ))
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Portfolio selection
( )( )( )...( )
b X b X b X
Growth-rate of wealth of a stock market portfolio b:
W(b,F) logbTxdF(x) E(logbTx)
*
W F W F
( )
max ( , )
b
* *
E S nW F
(log( ))
( ) n
b
1 1 2 2 3 3
1 1 2 2
1 1 2 2
n
n
n
n n
T T T
n n
T T T
n n
S
S
E S E E
E
b X b X b X
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Electrical Engineering Department
Portfolio selection – cont.
E S nW F
(log( )) ( )
1
( log( )) ( )
E S W F
Let be i.i.d. According to distribution F(x)
It can be shown using strong law of large numbers that
*( ) 2
nW F S
n
1 2 n X ,X , ...,X
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* *
* *
n
n
n
* . .1 * * 1 1
log ( log ) ( ) w p
n n S E S W F
n n
12. Sharif University of Technology
Electrical Engineering Department
Agenda
Why should we care about the stock market?
Information Theory and the Stock Market
Many works
Chen’s approach
Cover&Thomas’s approach
Concepts and Terminology
A sample result
Conclusion
12
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Electrical Engineering Department
Side Information
Suppose the broker has some information relevant to the
outcome of the stock.
What is the incrase in wealth that can result form such
information, i.e. the financial value of side information?
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Electrical Engineering Department
Incorporating Side Information
Let (X,Y) ~ f(x,y), X: market vector, Y: side information
I(X;Y) is an upper bound on the increase ΔW in growth rate.
W I (X;Y)
Thus, the financial value of side information is bounded by this
mutual information term.
15. Sharif University of Technology
Electrical Engineering Department
Agenda
Why should we care about the stock market?
Information Theory and the Stock Market
Many works
Chen’s approach
Cover&Thomas’s approach
Concepts and Terminology
A sample result
Conclusion
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Electrical Engineering Department
Conclusion
Motivated the Stock Market
Briefly discussed connections between Information
theory and Stock Market
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Electrical Engineering Department
References
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[1] T. Cover and J. Thomas. Elements of Information Theory. 2nd ed., John Wiley &
Sons, Inc., Hoboken, New Jersey. 2006.
[2] J. Chen, “Information Theory and Market Behavior”, SSRN, Dec 2003.
[3] J. Chen, “Information, Entropy And Evolutionary Finance” , SSRN, January
2003.
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Electrical Engineering Department
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Thanks For Your Time!