The Halloween indicator, “Sell in May and go Away”: an even bigger puzzle Ben Jacobsen* University of Edinburgh Business School
[email protected] Cherry Y. Zhang Nottingham University Business School, China
[email protected] Our simple new test for the Sell in May effect shows it not only defies stock market efficiency but also challenges the existence of a positive risk return trade off. When we examine the effect using all historical data for all stock market indices worldwide, we only find evidence of a significant positive ‘risk return’-trade-off during summer (May-October) in Mauritius. Pooling all country data we find excess returns during summer are significantly negative (-1.2% based on 33,348 monthly returns). Over the full year we find a positive estimate for the equity premium of 3.7% annually (t-value 7.65). * Corresponding Author: University of Edinburgh Business School, 29 Buccleuch Place, Edinburgh, Scotland EH8 9JS, United Kingdom, Tel: +44 131 651 5978 Electronic copy available at: http://ssrn.com/abstract=2154873 1. Introduction Since 2002 when Bouman and Jacobsen published their study on the Halloween Indicator, also known as the ‘Sell in May and go away’ effect, in the American Economic Review their study has stirred a fierce debate both in the academic literature and the popular press. Bouman and Jacobsen (2002) find that returns during winter (November through April) are significantly higher than during summer (May-October) in 36 out of the 37 countries in their study. As it was a new market efficiency anomaly they called it: ‘another puzzle’ One purpose of this paper is to rigorously re-examine the Halloween or Sell in May puzzle and address issues raised in the debate on data mining, sample selection bias, statistical problems, outliers and economic significance.1 More importantly, we also add a simple new test for this market wisdom.