The Evolution of Market Price Efficiency Around Earnings News

48 Pages Posted: 6 Feb 2018  

Charles Martineau

University of Toronto

Date Written: April 10, 2018


This paper studies the speed of price discovery following earnings announcements over 40 years. I use earnings surprises and the idiosyncratic volatility on announcement days to examine the responsiveness of stock prices to earnings news. For all stocks, financial markets have become more efficient at incorporating earnings news rapidly into stock prices over time. In the latter part of the sample period, post-earnings announcement drift is almost extinct. Improvements in the speed of price discovery coincide with the proliferation of news dissemination and to financial regulatory events, which I relate to the recent theory on market price efficiency.

Keywords: earnings announcements, idiosyncractic volatility, market efficiency, price discovery

JEL Classification: G10, G12, G14

Suggested Citation

Martineau, Charles, The Evolution of Market Price Efficiency Around Earnings News (April 10, 2018). Available at SSRN: or

Charles Martineau (Contact Author)

University of Toronto ( email )

105 St-George
Toronto, Ontario M5S3E6


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