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28 J. Corp. L. 635 (2002-2003)
The Mechanisms of Market Inefficiency: An Introduction to the New Finance

handle is hein.journals/jcorl28 and id is 645 raw text is: The Mechanisms of Market Inefficiency: An Introduction to
the New Finance
Lynn A. Stout*
Abstract
During the 1970s and early 1980s, the Efficient Capital Market Hypothesis (ECMH)
became one of the most widely-accepted and influential ideas in finance economics.
More recently, however, the idea of market efficiency has fallen into disrepute as a result
of market events and growing empirical evidence of inefficiencies. This essay argues that
the weaknesses of the efficient market theory are, and were, apparent from a careful
inspection of its initial premises, including the presumptions of homogeneous investor
expectations, effective arbitrage, and investor rationality. By the same token, a wide
range of market phenomena inconsistent with the ECHM can be explained using market
models that modify these three assumptions. In illustration, this Article explores three
important strands of today's finance literature: (1) the expanding body of work on asset
pricing when investors have heterogeneous expectations; (2) recent theoretical and
empirical scholarship on how and why arbitrage may move certain types of publicly
available information into price more slowly and incompletely than earlier writings
suggested; and (3) the exploding literature in behavioral finance, which examines what
happens to prices when market participants do not all share rational expectations. Taken
together, these three bodies of work show signs of providing the essential framework on
which a new and more powerful working model of securities markets can be built.
I.  IN T RO D U CT IO N  ....................................................................................................... 636
II. EFFICIENT MARKETS AND INVESTOR DISAGREEMENT ............................................ 639
III. EFFICIENT MARKETS AND THE LIMITS OF ARBITRAGE ........................................... 651
IV. EFFICIENT MARKETS AND INVESTOR IRRATIONALITY ............................................ 659
V .  C O N C LU SIO N  .......................................................................................................... 666
* Professor of Law, UCLA School of Law; Principal Investigator, UCLA-Sloan Foundation Research Program
on Business Organizations. An earlier version of this article was presented at the Journal of Corporation Law
Symposium on Revisiting the Mechanisms of Market Efficiency, held at The University of Iowa on April 4,
2003. I would like to thank the participants at that conference for their helpful suggestions. I am also especially
indebted to Bill Allen, Iman Anabtawi, Steven Bainbridge, Brian Cheffins, Allen Ferrell, Victor Fleischer, Ron
Gilson, David Hirshleifer, Peter Huang, Bill Klein, Reinier Kraakman, Jim Lindgren, Lynn LoPucki, and
Hillary Sale for their comments and insights on earlier drafts.

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