Testing For Speculative Bubbles In Stock Prices

Gerald P. Dwyer, Jr. and R. W. Hafer The articles and commentaries included in this volume were presented at the Federal Reserve Bank of St. Louis' thirteenth annual economic policy conference, held on October 21-22, 1988. The conference focused on the behavior of asset market prices, a topic of increasing interest to both the popular press and to academic journals as the bull market of the 1980s continued. The events that transpired during October, 1987, both in the United States and abroad, provide an informative setting to test alter native theories. In assembling the papers presented during this conference, we asked the authors to explore the issue of asset pricing and financial market behavior from several vantages. Was the crash evidence of the bursting of a speculative bubble? Do we know enough about the work ings of asset markets to hazard an intelligent guess why they dropped so dramatically in such a brief time? Do we know enough to propose regulatory changes that will prevent any such occurrence in the future, or do we want to even if we can? We think that the articles and commentaries contained in this volume provide significant insight to inform and to answer such questions. The article by Behzad Diba surveys existing theoretical and empirical research on rational bubbles in asset prices.

The papers in this book are grouped into three sections: the first on price bubbles is primarily financial; the second on speculative attacks (on exchange rate regimes) is international in scope; and the third, on policy switching, is concerned with monetary policy.

In the aftermath of the global financial crisis, the issue of how best to identify speculative asset bubbles (in real-time) remains in flux. This owes to the difficulty of disentangling irrational investor exuberance from the rational response to lower risk based on price behavior alone. In response, I introduce a two-pillar (price and quantity) approach for financial market surveillance. The intuition is straightforward: while asset pricing models comprise a valuable component of the surveillance toolkit, risk taking behavior, and financial vulnerabilities more generally, can also be reflected in subtler, non-price terms. The framework appears to capture stylized facts of asset booms and busts—some of the largest in history have been associated with below average risk premia (captured by the ‘pricing pillar’) and unusually elevated patterns of issuance, trading volumes, fund flows, and survey-based return projections (reflected in the ‘quantities pillar’). Based on a comparison to past boom-bust episodes, the approach is signaling mounting vulnerabilities in risky U.S. credit markets. Policy makers and regulators should be attune to any further deterioration in issuance quality, and where possible, take steps to ensure the post-crisis financial infrastructure is braced to accommodate a re-pricing in credit risk.

The presence of speculative bubbles in capital markets (an important area of interest in financial history) is widely accepted across many circles. Talk of them is pervasive in the media and especially in the popular financial press. Bubbles are thought to be found primarily in the stock market, which is our main interest, although bubbles are said to occur in other markets. Bubbles go hand in hand with the notion that markets can be irrational. The academic community has a great interest in bubbles, and it has produced scholarly literature that is voluminous. For some economists, doing bubble research is like joining the vanguard of a Kuhnian paradigm shift in economic thinking. Not so fast. If bubbles did exist, they would pose a serious challenge to neoclassical finance. Bubbles would contradict the ideas that markets are rational or work in an informationally efficient manner. That’s what makes the topic of bubbles interesting. This book reviews and evaluates the academic literature as well as some popular investment books on the possible existence of speculative bubbles in the stock market. The main question is whether there is convincing empirical evidence that bubbles exist. A second question is whether the theoretical concepts that have been advanced for bubbles make them plausible. The reader will discover that I am skeptical that bubbles actually exist. But I do not think I or anyone else will ever be able to conclusively prove that there has never been a bubble. From studying the literature and from reading history, I find that many famous purported bubbles reflect inaccurate history or mistakes in analysis or simply cannot be shown to have existed. In other instances, bubbles might have existed. But in each of those cases, there are credible rational explanations. And good evidence exists for the idea that even if bubbles do exist, they are not of great importance to understanding the stock market.

Examining the role of speculative bubbles in the stock market, this text argues that, provided they are sustainable, bubbles may have a positive effect on the market. They may provide additional investment opportunities with the potential to increase aggregate profits and improve economic welfare.