The virtues and vices of equilibrium and the future of financial economics

The use of equilibrium models in economics springs from the desire for parsimonious models of economic phenomena that take human reasoning into account. This approach has been the cornerstone of modern economic theory. We explain why this is so, extolling the virtues of equilibrium theory; then we present a critique and describe why this approach is inherently limited, and why economics needs to move in new directions if it is to continue to make progress. We stress that this shouldn't be a question of dogma, but should be resolved empirically. There are situations where equilibrium models provide useful predictions and there are situations where they can never provide useful predictions. There are also many situations where the jury is still out, i.e., where so far they fail to provide a good description of the world, but where proper extensions might change this. Our goal is to convince the skeptics that equilibrium models can be useful, but also to make traditional economists more aware of the limitations of equilibrium models. We sketch some alternative approaches and discuss why they should play an important role in future research in economics.Comment: 68 pages, one figur

"Causes of Financial Instability: Don’t Forget Finance"

Given the economy's complex behavior and sudden transitions as evidenced in the 2007–08 crisis, agent-based models are widely considered a promising alternative to current macroeconomic practice dominated by DSGE models. Their failure is commonly interpreted as a failure to incorporate heterogeneous interacting agents. This paper explains that complex behavior and sudden transitions also arise from the economy's financial structure as reflected in its balance sheets, not just from heterogeneous interacting agents. It introduces "flow-of-funds" and "accounting" models, which were preeminent in successful anticipations of the recent crisis. In illustration, a simple balance-sheet model of the economy is developed to demonstrate that nonlinear behavior and sudden transition may arise from the economy’s balance-sheet structure, even without any microfoundations. The paper concludes by discussing one recent example of combining flow-of-funds and agent-based models. This appears a promising avenue for future research.Credit Crisis; Finance; Complex Systems; DSGE; Agent-based Models; Stock-flow Consistent Models

The Tobin Tax A Review of the Evidence

The debate about the Tobin Tax, and other financial transaction taxes (FTT), gives rise to strong views both for and against. Unfortunately, little of this debate is based on the now considerable body of evidence about the impact of such taxes. This review attempts to synthesise what we know from the available theoretical and empirical literature about the impact of FTTs on volatility in financial markets. We also review the literature on how a Tobin Tax might be implemented, the amount of revenue that it might realistically produce, and the likely incidence of the tax. We conclude that, contrary to what is often assumed, a Tobin Tax is feasible and, if appropriately designed, could make a significant contribution to revenue without causing major distortions. However, it would be unlikely to reduce market volatility and could even increase it.Tobin tax, financial transaction taxes, volatility, revenue, incidence, feasibility

The Virtues and Vices of Equilibrium and the Future of Financial Economics

The use of equilibrium models in economics springs from the desire for parsimonious models of economic phenomena that take human reasoning into account. This approach has been the cornerstone of modern economic theory. We explain why this is so, extolling the virtues of equilibrium theory; then we present a critique and describe why this approach is inherently limited, and why economics needs to move in new directions if it is to continue to make progress. We stress that this shouldn’t be a question of dogma, but should be resolved empirically. There are situations where equilibrium models provide useful predictions and there are situations where they can never provide useful predictions. There are also many situations where the jury is still out, i.e., where so far they fail to provide a good description of the world, but where proper extensions might change this. Our goal is to convince the skeptics that equilibrium models can be useful, but also to make traditional economists more aware of the limitations of equilibrium models. We sketch some alternative approaches and discuss why they should play an important role in future research in economics.Equilibrium, Rational expectations, Efficiency, Arbitrage, Bounded rationality, Power laws, Disequilibrium, Zero intelligence, Market ecology, Agent based modeling

Econophysics: agent-based models

This article is the second part of a review of recent empirical and theoretical developments usually grouped under the heading Econophysics. In the first part, we reviewed the statistical properties of financial time series, the statistics exhibited in order books and discussed some studies of correlations of asset prices and returns. This second part deals with models in Econophysics from the point of view of agent-based modeling. Of the large number of multiagent- based models, we have identified three representative areas. First, using previous work originally presented in the fields of behavioral finance and market microstructure theory, econophysicists have developed agent-based models of order-driven markets that we discuss extensively here. Second, kinetic theory models designed to explain certain empirical facts concerning wealth distribution are reviewed. Third, we briefly summarize game theory models by reviewing the now classic minority game and related problems.

Performativity and Financial Markets: Option Pricing in the Late 19th Century

The paper revisits the performativity thesis in economics stressing the plural character of knowledge, which includes not only scientific models but also every form of practical knowledge that systematizes the visible and the articulable experience of economic agents. To highlight the point, the paper examines the pricing of options in London in the late 19th century, long before the academic origin of modern option pricing models. The pamphlets of the time are valuable archives of existing option transactions performed on the basis of systematic practical techniques widely established among investors

Why the Law Hates Speculators: Regulation and Private Ordering in the Market for OTC Derivatives

A wide variety of statutory and common law doctrines in American law evidence hostility towards speculation. Conventional economic theory, however, generally views speculation as an efficient form of trading that shifts risk to those who can bear it most easily and improves the accuracy of market prices. This Article reconciles the apparent conflict between legal tradition and economic theory by explaining why some forms of speculative trading may be inefficient. It presents a heterogeneous expectations model of speculative trading that offers important insights into antispeculation laws in general, and the ongoing debate concerning over-the-counter (OTC) derivatives in particular. Although trading in OTC derivatives is presently largely unregulated, the Commodity Futures Trading Commission recently announced its intention to consider substantively regulating OTC derivatives under the Commodity Exchange Act (CEA). Because the CEA is at heart an antispeculation law, the heterogeneous expectations model of speculation offers policy support for the CFTC\u27s claim of regulatory jurisdiction. This model also, however, suggests an alternative to the apparently binary choice now available to lawmakers (i. e., either regulate OTC derivatives under the CEA, or exempt them). That alternative would be to regulate OTC derivatives in the same manner that the common law traditionally regulated speculative contracts: as permitted, but legally unenforceable, agreements. By requiring derivatives traders to rely on private ordering to ensure the performance of their agreements, this strategy may offer significant advantages in discouraging welfare-reducing speculation based on heterogeneous expectations while protecting more beneficial forms of derivatives trading