Securities Law Prof Blog

Editor: Eric C. Chaffee
Univ. of Toledo College of Law

Sunday, September 9, 2012

Bhattacharya & O'Brien on Market Efficiency

Arbitrage Risk and Market Efficiency – Applications to Securities Class Actions, by Rajeev R. Bhattacharya, Berkeley Research Group, and Stephen Jerome O'Brien was recently posted on SSRN.  Here is the abstract:

Measuring the efficiency of the market for a stock is important for a number of reasons. For example, it determines the necessity for an investor to acquire expensive additional information about a firm, and it is a critical factor in class certification in a securities class action. We provide a general methodology to measure the market efficiency percentile for a stock for any relevant period. We apply this methodology to calculate arbitrage risk for each U.S. exchange-listed common stock for every calendar year from 1988 to 2010. We find that market efficiency is significantly affected by turnover (negatively), the number of market makers for Nasdaq stocks (negatively), and serial correlation in the market model of the stock (positively). These findings seem inconsistent with β€œconventional wisdom,” but we show that our findings are consistent with economic logic. The relations between market efficiency and market capitalization (positive), bid-ask spread (negative), institutional ownership (positive), and explanatory power of the relevant market model (positive) are consistent with conventional wisdom. The impact on market efficiency of the number of securities analysts following a stock and the public float ratio of a stock are of ambiguous significance.

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