The Myth of the Rational Market: A History of Risk, Reward, and Delusion on Wall Street
Book Details
- Author: Justin Fox
- Categories: Market Theory, Behavioral Finance, Financial History
Quick Summary
Justin Fox traces the intellectual history of the efficient market hypothesis from Irving Fisher through Eugene Fama, and its eventual challenge by behavioral economists like Richard Thaler and Robert Shiller, revealing how the belief in rational markets shaped and ultimately failed Wall Street.
Detailed Summary
"The Myth of the Rational Market" by Justin Fox is a sweeping intellectual history that chronicles the rise and partial fall of the efficient market hypothesis (EMH), the idea that financial asset prices always accurately reflect all available public information. Fox structures the narrative chronologically around the key academic figures who built, tested, challenged, and partially dismantled the theory of market rationality.
The book opens with "Early Days," covering Irving Fisher's pioneering but ultimately disastrous attempts to apply reason and science to markets in the early 20th century, and the statistical work of Fred Macaulay and Holbrook Working that laid mathematical foundations in the 1930s. "The Rise of the Rational Market" follows Harry Markowitz's introduction of modern portfolio theory (assembled from poker strategy and World War II gunnery experience), Paul Samuelson's development of the random walk proposition, Modigliani and Miller's simplifying assumptions that transformed corporate finance, and Gene Fama's articulation of the efficient markets hypothesis at the University of Chicago.
"The Conquest of Wall Street" documents how these academic ideas transformed practice: Jack Bogle's creation of index funds, Fischer Black's work on options pricing and risk measurement, and Michael Jensen's application of market efficiency to corporate governance (leading to the hostile takeover era). The narrative then shifts to "The Challenge," chronicling Dick Thaler's introduction of behavioral economics, Bob Shiller's demonstration that market volatility far exceeds what rational models predict, and the evidence that investors like Warren Buffett and Ed Thorp consistently beat the market.
"The Fall" covers the intellectual triumph of the EMH's critics, led by Andrei Shleifer's work showing why irrational market forces can be as pervasive as rational ones, Jensen's own change of mind about corporate governance, and the ongoing debate between Fama and Thaler. The epilogue examines the 2008 financial crisis through the lens of this intellectual history, beginning with Alan Greenspan's admission to Congress that his worldview -- built on forty years of market rationality assumptions -- had proven fundamentally wrong. Fox's account reveals that the debate over market rationality has ended "in something more than a draw and less than a resounding victory" for either side.
