University of Oulu

Essays on the effects of gains and losses on the trading behavior of individual investors in the Finnish stock market

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Author: Lehenkari, Mirjam1
Organizations: 1University of Oulu, Faculty of Economics and Business Administration, Department of Accounting and Finance
Format: ebook
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 0.6 MB)
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Language: English
Published: 2009
Publish Date: 2009-03-03
Thesis type: Doctoral Dissertation
Defence Note: Academic dissertation to be presented, with the assent of the Faculty of Economics and Business Administration of the University of Oulu, for public defence in Auditorium TA105, Linnanmaa, on March 13th, 2009, at 12 noon
Reviewer: Professor Timo Rothovius
Professor Hersh Shefrin


The behavior of investors is often at odds with the assumptions of traditional finance theory. Research conducted over the past half-century or so abounds with examples in which the central axioms of traditional theory are systematically violated. One of the most well-established behavioral patterns in this context is the disproportionate tendency of investors to sell stocks that have appreciated in value since purchase (‘winners’) rather than stocks that have declined in value (‘losers’); this phenomenon is known as the disposition effect and most commonly attributed to Kahneman and Tversky’s (1979) prospect theory. The overall aim of this doctoral thesis is to investigate the robustness of this phenomenon, its underlying mechanisms, and its potential implications for individual investors.

The four independent but related essays of this thesis were designed to answer the following research questions: (1) Does the disposition effect ‘survive’ bear markets, in which investors may not be able to realize gains even if they wish to do so? (2) Is there any supporting evidence for prospect theory-based explanation of the disposition effect in the form of other observed behavior consistent with the theory? (3) Is prospect theory the most feasible explanation for the disposition effect? (4) What are the implications of the disposition effect from the point of view of individual investors?

Using comprehensive data covering virtually all trades executed in the Finnish stock market during 1995–2003, this thesis demonstrates the following: (1) As robust as the disposition effect appears to be in light of previous studies, the phenomenon is only partially detected in bear markets. (2) The relationship between prospect theoretic preferences and investor behavior is not easily generalizable to other behavioral patterns besides the disposition effect. (3) In fact, even the relationship between prospect theory and the disposition effect is not as strong as is generally believed. Our results instead suggest an explanation based on escalation of commitment, according to which the disposition effect is caused above all by self-justificatory concerns. (4) Finally, although the disposition effect is generally inconsistent with economic rationality, it does not appear to be detrimental to investment performance.

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Series: Acta Universitatis Ouluensis. G, Oeconomica
ISSN-E: 1796-2269
ISBN: 978-951-42-9045-9
ISBN Print: 978-951-42-9044-2
Issue: 37
Copyright information: © University of Oulu, 2009. This publication is copyrighted. You may download, display and print it for your own personal use. Commercial use is prohibited.