Shiller credits an unprecedented confluence of events with driving stocks to uncharted heights. He analyzes the structural and psychological factors that explain why the Dow Jones Industrial Average tripled between 1994 and 1999, a level of growth not reflected in any other sector of the economy. In contrast to many analysts, Shiller stresses circumstances that alter investors' perceptions of the market. These include the entry of the Internet into American homes, the misimpression that the aging of the baby-boom generation builds long-term protection into the market, and herd behavior, such as day-trading. He also examines cultural factors, including sports-style media coverage of the Dow's ups and downs and "new era" thinking about the economy. He considers—and challenges—efforts to rationalize exuberance that are based on either efficient-markets theory, narrowly construed, or the claim that investors have only recently learned the true value of the market.

In the most controversial portion of the book, Shiller cautions that a market that is overvalued by historical standards is inherently precarious. Among his prescriptions is an urgent plea to immediately end what he argues are perilous schemes to privatize social security in favor of plans to reformit. He also argues that private pension plans that encourage many people to put their entire retirement funds in the stock market should be modified. And he calls on our savings and investment institutions to take more sensible account of emerging risk-management principles. Shiller's analysis is convincingly documented, and—regardless of the market's future behavior—his book will stand as an important elaboration of why stocks soared and what our investment alternatives are.