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This portfolio selection study compares the performance of universal and non-universal algorithms for investing in the stock market. The study uses real data from the stock market to analyze various strategies and provide insights on building a successful portfolio.
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PORTFOLIO SELECTION:experimental comparison of Universal and non-universal Algorithms Lorenzo Coviello and Petros Mol Universal Information Processing, Spring 2011 June 2, 2011
Motivation • Investing money in the stock market • How to build a successful portfolio? • Compare various strategies
Introduction • Universal portfolio selection: provides guarantees on wealth growth rate • Real market: invest in the most profitable way • Compare performance of portfolio selection criteria on real data from the stock market
Rest of the talk • Introduction • Portfolio selection: the model • Methodology • Two approaches • Reversal to the mean • Trend is your friend • Simulations - Comparison
The model – price relatives • Portfolio:m stocks • Trading period: T trading days • Xij: price relative of stock j at day i • Xi often assumed i.i.d. (strong assumption)
The model - wealth • Portfolio at day i • The wealth gain in one day • The overall wealth gain in T days
The model - strategy • How to distribute the wealth among the stocks? • Decision problem: choose a portfolio each day
Rest of the talk • Introduction • Portfolio selection: the model • Methodology • Two approaches • Reversal to the mean • Trend is your friend • Comparison
Methodology • Data Collected from Yahoo! finance • Adjusted close price used • Period: 1996- 2010 • 3778 trading days • No priors on the stocks, no fundamentals • No transaction costs
Portfolio: List of Stocks • Tech(11) : AMD, Apple, AT&T, Cisco, Dell, HP, IBM, Intel, Microsoft, Nokia, Oracle • Finance(7):American Express, Bank of America, Barclay’s, Citigroup, JP Morgan, Morgan Stanley, Wells Fargo • Other (12) : Boeing , BP, Coca-Cola Company, Exxon, Ford, General Electric, J&J, McDonalds, Pfizer, P&G, Wall Mart, Walt Disney
Rest of the talk • Introduction • Portfolio selection: the model • Methodology • Two approaches • Reversal to the mean • Trend is your friend • Comparison
Two main approaches • Reversal to mean • Assume stock growth rates stable in the long run, and • Occasional larger returns followed by smaller rates • CRP, Semi-CRP, ANTICOR • Trend is your friend • Portfolio based on recent stock performance • Histogram portfolio selection, kernel portfolio selection
Buy and hold • Build portfolio once, let the wealth grow • Uniform buy and hold (U-BAH) • Performance guarantees for U-BAH • Best BAH in hindsight: invest on the best stock
Rest of the talk • Introduction • Portfolio selection: the model • Methodology • Two approaches • Reversal to the mean • Trend is your friend • Comparison
Reverse to mean approach Assumptions • Stock growth rates stable in the long run • Occasional larger returns followed by smaller rates, and vice versa
Constant rebalancing portfolio • Rebalance portfolio every day according to pmfb • Uniform CRP: • Exponential gain if “reversal to the mean” market • Stock 1: constant value • Stock 2: doubles on odd days, halves on even days • Uniform CRP • Wealth grows of 1/8 every 2 days • Best CRP in hindsight difficult to compute
Semi-constant rebalanced portfolio • Reference: Kalai (1998), Helmbold (1998), Kozat (2009) • Portfolio rebalanced every arbitrary period • Rebalancing period can be fixed • Real market: reduced commissions
Semi-constant rebalanced portfolio • Consider rebalancing every d days • Uniform target distribution • The wealth before rebalancing for the kth time
Semi-CRP with deviation control • Ref. Kozat (2009) • Idea: avoid useless rebalancing • Rebalance only if large distance between target portfolio b and current wealth distribution w
ANTICOR algorithm • Reference: Borodin, El-Yaniv, Gogan (2004) • Aggressive “reversal to the mean” • Transfer money from stock i to stock j if • Growth of stock i > growth of stock j over last window • Stock i in second last window and stock j in last window positively correlated
ANTICOR algorithm • Define • Averages of columns of LXk
ANTICOR algorithm • Cross correlation • stock iover the second last window • stock j over the last window • Normalization
ANTICOR algorithm • Transfer money from stock i to stock j if • In an amount proportional to
Rest of the talk • Introduction • Portfolio selection: the model • Methodology • Two approaches • Reversal to the mean • Trend is your friend • Comparison
The trend is your friend • Portfolio based on stock performance • Prefer performing (trendy) stocks • Use the market history to determine the current portfolio
Histogram portfolio selection • Ref: Gyorfi and Schafer (2003) • Rectangular window of width w days • Distribute the wealth uniformly among k best stocks
Kernelportfolio selection • Higher weight to the recent past • Window size of w days • Window shape • Linear • Exponential • Example: score of stock j at day i+1
Kernel portfolio selection • Each day the scores determine the portfolio • Examples • Follow the best stock • Uniform distribution between k best stock • Proportional to score for best k stocks
Conclusion Put all your money in Anticor! But choose the right window!!!
THANKS Lorenzo Coviello and PetrosMol