The Myth of the Rational Market

Justin Fox’s The Myth of the Rational Market tells the story of how we came to believe that financial markets knew best, and how that belief steered us wrong. Chronicling the rise and fall of efficient market theory and its century-long role in the making of the modern financial industry, the book is both history and intellectual whodunit. It brings to life the people and ideas that forged modern finance and investing, from the Great Depression and into the financial calamity of today. It’s a tale largely about professors, but professors who made and lost fortunes, battled fiercely over ideas, beat the house in blackjack, wrote bestselling books, and played major roles on the world stage. It’s also a tale of Wall Street’s evolution, the power of the market to generate wealth and wreak havoc, and free-market capitalism’s recurrent war with itself.

The efficient market hypothesis—long part of academic folklore but codified in the 1960s at the University of Chicago—has evolved into a powerful myth. It has been the driver of trillions of investing dollars, the inspiration for index funds and vast new derivatives markets. In its strongest form, the theory holds that the decisions of millions of investors, all digging for information and striving for an edge, inevitably add up to rational, perfect markets. That belief has crumbled.

Celebrated journalist Fox introduces a new wave of scholars who no longer teach that investors are rational or that markets are always right. Many now agree with Yale professor Robert Shiller that efficient market theory “represents one of the most remarkable errors in the history of economic thought.” Today the theory is giving way to new hypotheses of market behavior growing out of psychology, physics, evolutionary biology—and even traditional economics. In his landmark intellectual history, Fox uncovers the new ideas that may drive markets in the century ahead.