This paper extends previous work on speculative dynamics in the foreign exchange market. The analysis shows how the behavior of chartists, fundamentalists and rational speculators, together with uncertainty about the long-run equilibrium exchange rate level, can result in fluctuations of the spot rate triggered by a random shock to the market. Although the exact exchange rate path depends on the extent of the shock and on specific values of model parameters, the heterogeneity of expectations can explain several characteristics of short-term exchange rate developments, which have often been emphasized in empirical studies on exchange rate dynamics.

I began serious consideration of the issues and subject matter that comprise this book as a graduate student at the University of Massachusetts at Amherst. In need of a dissertation topic and vaguely curious about international monetary economics, I decided to sit in on Leonard Rapping's undergraduate course on international finance. Needless to say, I was soon hooked. Within several months I was teaching my own course on international money and beginning to write an outline of what would become my doctoral dissertation on foreign exchange speculation. Once completed the dissertation thesis became this basis for this book.

For about three decades until the Global Financial Crisis (GFC), Covered Interest Parity (CIP) appeared to hold quite closely—even as a broad macroeconomic relationship applying to daily or weekly data. Not only have CIP deviations significantly increased since the GFC, but potential macrofinancial drivers of the variation in CIP deviations have also become significant. The variation in CIP deviations seems to be associated with multiple factors, not only regulatory changes. Most of these do not display a uniform importance across currency pairs and time, and some are associated with possible temporary considerations (such as asynchronous monetary policy cycles).

A new view of the economy as an evolving, complex system has been pioneered at the Santa Fe Institute over the last ten years, This volume is a collection of articles that shape and define this view?a view of the economy as emerging from the interactions of individual agents whose behavior constantly evolves, whose strategies and actions are always adapting.The traditional framework in economics portrays activity within an equilibrium steady state. The interacting agents in the economy are typically homogenous, solve well-defined problems using perfect rationality, and act within given legal and social structures. The complexity approach, by contrast, sees economic activity as continually changing?continually in process. The interacting agents are typically heterogeneous, they must cognitively interpret the problems they face, and together they create the structures?markets, legal and social institutions, price patters, expectations?to which they individually react. Such structures may never settle down. Agents may forever adapt and explore and evolve their behaviors within structures that continually emerge and change and disappear?structures these behaviors co-create. This complexity approach does not replace the equilibrium one?it complements it.The papers here collected originated at a recent conference at the Santa Fe Institute, which was called to follow up the well-known 1987 SFI conference organized by Philip Anderson, Kenneth Arrow, and David Pines. They survey the new study of complexity and the economy. They apply this approach to real economic problems and they show the extent to which the initial vision of the 1987 conference has come to fruition.

In traditional economics models of perfect competition agent's interactions are all mediated through the market. Interactions are anonymous, global and indirect. This is a powerful model, but we see many instances in which one, and sometimes all, of the previous characteristics fail to hold true. The type of agent you are, or your identity, can affect the type of interaction we have, and most surely the relationship between micro-behaviour and macro-phenomena in non-trivial ways. This book contains a selection of papers presented at the 6th Workshop on Economics with Heterogenous Interacting Agents (WEHIA). The contributions show that work done in other fields like evolutionary biology, statistical mechanics, social network theory and others help us to understand the way in which economic systems operate. Virtually all of the papers presented in this volume draw on some aspect or other of these varied approaches to related problems.