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Beta Estimate of High Frequency Data. Angela Ryu Economics 201FS Honors Junior Workshop: Finance Duke University March 3, 2010. Data. XOM (Exxon Mobile) Dec 1 1999 – Jan 7 2009 (2264 days) GOOG (Google) Aug 20 2004 – Jan 7 2009 (1093 days) WMT (Wal-Mart)
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Beta Estimate of High Frequency Data Angela Ryu Economics 201FS Honors Junior Workshop: Finance Duke University March 3, 2010
Data • XOM (Exxon Mobile) • Dec 1 1999 – Jan 7 2009 (2264 days) • GOOG (Google) • Aug 20 2004 – Jan 7 2009 (1093 days) • WMT (Wal-Mart) • Apr 9 1997 – Jan 7 2009 (2921 days) FOR ALL 3 stocks
Motivation • Multivariate Measures: Beta • Problem of balancing bias/precision • High frequency sampling: biased, due to microstructure noise • Low frequency sampling: imprecise • Theoretical approach requires more background knowledge approach empirically!
Preparation • Interday returns are excluded • Beta calculated from: (for βX = Y, X,Y stock prices) • Sampling intervals: 1 to 20 minutes • Beta Calculation intervals: 1 to 50 days • Mean Squared Error calculated for each Beta interval • MSE of GOOG(X) vs. XOM(Y) , 30 days interval?= Average of Squared Errors of each days predicted by using β i.e. ypre_day31 = βday1_30 * xact_day31 SEday31 = (ypre_day31 – yact_day31 )2 ypre_day32 = βday2_31 * xact_day32 SEday32 = (ypre_day32 – yact_day32 )2 … MSE30 = avg(SEday31 ,SEday32 , ... SEday1093 )
Results • 5 – 15 days interval for Beta gave least MSE for many stock pairs, for most sampling intervals • As the sampling interval increased, MSE for shorter Beta intervals increased rapidly • For 20 min. sampling interval, there is less increase of MSE as increase in Beta interval compared to shorter sampling intervals
Analysis • Against our intuition: why would more information harm prediction of the price? • Possible interpretation • Given a sampling interval, after a certain range of “information” gather for Beta estimation, say 5 – 15 days, more information distorts the prediction • On the other hand, some short Beta intervals (e.g. 1 day, 2 days) for longer sampling intervals may be insufficient and result in high MSE
Questions & Further Steps • Theoretical evidence? Any relevant papers? • Is the estimator biased? Why? • What is the role of Microstructure noise? • Check calculations. Try with other stocks or possibly portfolios (industry/macroeconomic factors) • Use Realized Beta and compare the results Andersen, Bollerslev, Diebold and Wu (2003)