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William A. Reese, Jr. Russell P. Robins A. B. Freeman School of Business Tulane University FEA Conference Sept. 25, 2015 1
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2 When there is an announcement of a corporate acquisition, the price of the firm being acquired usually goes up. The price of the firm making the acquisition usually goes down When an analyst upgrades a stock, it usually goes up in price Initial Public Offerings (IPOs) of common stock are usually underpriced.
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3 It is difficult to make money based on some surprising economic data a day or two after the data has been released. Historically, on average, small-cap stocks do well in the month of January. There are various types of momentum in stock returns (weekly, monthly, longer) Investors tend to put more money into mutual funds that have recently performed well.
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4 Each of these facts have been found by researchers through Event Studies Plotting Cumulative Abnormal Returns (CARs) make Event Studies easy to explain and understand
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We teach the facts We show the graphs We don’t teach the methodology It can be complex We don’t have students do their own Event Studies What to do? Time consuming 8
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Investments Course Undergrad or MBA Easy to Perform Easy to Understand Predictable Results 9
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Are there abnormal returns when a stock is added to the S&P 500? Is there abnormal trading volume? 10
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Since October 1989, S&P has been announcing (when possible) changes to the index one week prior to the effective date Index funds MUST buy the stock May create upward price pressure 11
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Every stock that was added to the S&P 500 between January 2000 and July 2015. Purged to leave 270 stocks that are still listed on Yahoo! Finance Date of addition Ticker symbol 12
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Macro that obtains data from Yahoo! Finance for stocks the student selects and S&P 500 42 days before the listing date 10 days after the listing date 13
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Event window is day -10 to day +10 Returns for stock and S&P are calculated for 30 days prior to event window “Calculation Period” 14
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A regression estimates alpha and beta for each stock during calculation period: R i = α + β(R Mkt ) + e. These estimates are used to calculate risk- adjusted expected returns during the event window: E(R)= α + β(R Mkt ) 15
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Abnormal returns are calculated: Abn. R i = R i - E(R i ) Cumulative Abnormal Returns (CARs) are the sum of all abnormal returns up to time t in the event window 16
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Cumulative Abnormal (Scaled) Volume is also calculated for the event window Average volume during calculation period is established as “normal” volume CARs and CAVs are averaged across stocks in the sample and T-stats are calculated. 17
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Select a random set of stocks from our list Enter their ticker symbols into spreadsheet Click “Download” Wait a couple of minutes Depending on internet speed and number of stocks selected Observe and analyze the results Answer prepared questions Come up with their own idea for an event study 20
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How an event study is done How to calculate risk-adjusted returns using the market model How to calculate and plot CARs Reinforcement of averages, standard errors, t-stats, and statistical significance How buying pressure can affect returns and volume 21
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The Spreadsheet and basic instructions can be found at http://info.freeman.tulane.edu/breeseemba/eventstudy.htm 22
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