Bubbles Rational Expectations And Financial Markets

This paper investigates the nature and the presence of bubbles in financial markets. Are bubbles consistent with rationality? If they are, do they, like Ponzi games, require the presence of new players forever? Do they imply impossible events in finite time, such as negative prices? Do they need to go on forever to be rational? Can they have real effects? These are some of the questions asked in the first three sections. The general conclusion is that bubbles, in many markets, are consistent with rationality, that phenomena such as runaway asset prices and market crashes are consistent with rational bubbles. In the last two sections, we consider whether the presence of bubbles in a particular market can be detected statistically. The task is much easier if there are data on both prices and returns. In this case, as shown by Shiller and Singleton, the hypothesis of no bubble implies restrictions on their joint distribution and can be tested. In markets in which returns are difficult to observe, possibly because of a nonpecuniary component, such as gold, the task is more difficult. We consider the use of both "runs tests" and "tail tests" and conclude that they give circumstantial evidence at best.

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.

Economists broadly define financial asset price bubbles as episodes in which prices rise with notable rapidity and depart from historically established asset valuation multiples and relationships. Financial economists have for decades attempted to study and interpret bubbles through the prisms of rational expectations, efficient markets, and equilibrium, arbitrage, and capital asset pricing models, but they have not made much if any progress toward a consistent and reliable theory that explains how and why bubbles (and crashes) evolve and can also be defined, measured, and compared. This book develops a new and different approach that is based on the central notion that bubbles and crashes reflect urgent short-side rationing, which means that, as such extreme conditions unfold, considerations of quantities owned or not owned begin to displace considerations of price.

3 On the Economic Relevance of Rational Bubbles 79 3. 1 Capital markets . . . . . . . . . 80 3. 1. 1 Efficient capital markets 86 3. 1. 2 Rational bubbles on capital markets. 93 3. 1. 3 Economic caveats . 103 3. 2 Foreign exchange markets 109 3. 3 Hyperinflation. . . . . . . 117 4 On Testing for Rational Bubbles 123 4. 1 Indirect tests . . . . . . . . . 123 4. 1. 1 Variance bounds tests 124 4. 1. 2 Specification tests . . . 137 4. 1. 3 Integration and cointegration tests 140 4. 1. 4 Final assessment of indirect tests . 150 4. 1. 5 A digression: Charemza, Deadman (1995) analysis. 151 4. 2 Direct tests . . . . . . . . . . . . . . . . . . . . . . . . 157 4. 2. 1 Deterministic bubble in German hyperinflation. 158 4. 2. 2 Intrinsic bubbles on stock markets. 163 4. 2. 3 An econometric caveat . . . . . 168 4. 2. 4 Final assessment of direct tests 172 5 On the Explanatory Power of Rational Bubbles on the G- man Stock Market 175 5. 1 Data . . . . . . . 175 5. 2 Direct test for rational bubbles 181 5. 2. 1 Temporary Markovian bubbles. 184 5. 2. 2 Temporary intrinsic bubbles . . 193 ix 5. 2. 3 Permanent intrinsic bubbles 198 5. 3 A digression: Testing for unit roots 204 6 Concluding Remarks 215 A Results 221 A. 1 Temporary markovian bubbles. 221 A. 2 Temporary intrinsic bubbles . . 225 A. 3 Permanent intrinsic bubbles - Class 1 to 2 229 A. 4 Permanent intrinsic bubbles - Class 3 to 6 230 A. 5 Integration tests. . . . . . . . . . . . . . .

Economists broadly define financial asset price bubbles as episodes in which prices rise with notable rapidity and depart from historically established asset valuation multiples and relationships. Financial economists have for decades attempted to study and interpret bubbles through the prisms of rational expectations, efficient markets, equilibrium, arbitrage, and capital asset pricing models, but they have not made much if any progress toward a consistent and reliable theory that explains how and why bubbles (and crashes) evolve and are defined, measured, and compared. This book develops a new and different approach that is based on the central notion that bubbles and crashes reflect urgent short-side rationing, which means that, as such extreme conditions unfold, considerations of quantities owned or not owned begin to displace considerations of price.

This book describes a laboratory experiment designed to test the causes and properties of bubbles in financial markets and explores the question whether it is possible to design markets which avoid such bubbles and crashes. In the experiment, subjects were given the opportunity to trade in a stock market modeled after the seminal work of Smith et al. (1988). To account for the increasing importance of online betting sites, subjects were also allowed to trade in a digital option market. The outcomes shed new light on how subjects form and update their expectations, placing special emphasis on the bounded rationality of investors. Various analytical bubble measures found in the literature are collected, calculated, classified and presented for the first time. The very interesting new bubble measures "Dispersion Ratio", "Overpriced Transactions" and "Underpriced Transactions" are developed, making the book an important step towards the research goal of preventing bubbles and crashes in financial markets.

The role of information is central to the academic debate on finance. This book provides a detailed, current survey of theoretical research into the effect on stock prices of the distribution of information, comparing and contrasting major models. It examines theoretical models that explain bubbles, technical analysis, and herding behavior. It also provides rational explanations for stock market crashes. Analyzing the implications of asymmetries in information is crucial in this area. This book provides a useful survey for graduate students.

A powerful challenge to contemporary economics and a new agenda for global finance In the wake of the global financial crisis that began in 2007, faith in the rationality of markets has lost ground to a new faith in their irrationality. The problem, Roman Frydman and Michael Goldberg argue, is that both the rational and behavioral theories of the market rest on the same fatal assumption—that markets act mechanically and economic change is fully predictable. In Beyond Mechanical Markets, Frydman and Goldberg show how the failure to abandon this assumption hinders our understanding of how markets work, why price swings help allocate capital to worthy companies, and what role government can and can't play. The financial crisis, Frydman and Goldberg argue, was made more likely, if not inevitable, by contemporary economic theory, yet its core tenets remain unchanged today. In response, the authors show how imperfect knowledge economics, an approach they pioneered, provides a better understanding of markets and the financial crisis. Frydman and Goldberg deliver a withering critique of the widely accepted view that the boom in equity prices that ended in 2007 was a bubble fueled by herd psychology. They argue, instead, that price swings are driven by individuals' ever-imperfect interpretations of the significance of economic fundamentals for future prices and risk. Because swings are at the heart of a dynamic economy, reforms should aim only to curb their excesses. Showing why we are being dangerously led astray by thinking of markets as predictably rational or irrational, Beyond Mechanical Markets presents a powerful challenge to conventional economic wisdom that we can't afford to ignore.