ABSTRACT Economists not only failed to anticipate the financial crisis; they may have contributed to it—with risk and derivatives models that, through spurious precision and untested theoretical assumptions, encouraged policy makers and market participants to see more stability and risk sharing than was actually present. Moreover, once the crisis occurred, it was met with incomprehension by most economists because of models that, on the one hand, downplay the possibility that economic actors may exhibit highly interactive behavior; and, on the other, (...) assume that any homogeneity will involve economic actors sharing the economist’s own putatively correct model of the economy, so that error can stem only from an exogenous shock. The financial crisis presents both an ethical and an intellectual challenge to economics, and an opportunity to reform its study by grounding it more solidly in reality. (shrink)

The economic crisis is also a crisis for economic theory. Most analyses of the evolution of the crisis invoke three themes, contagion, networks and trust, yet none of these play a major role in standard macroeconomic models. What is needed is a theory in which these aspects are central. The direct interaction between individuals, firms and banks does not simply produce imperfections in the functioning of the economy but is the very basis of the functioning of a modern economy. This (...) book suggests a way of analysing the economy which takes this point of view. The economy should be considered as a complex adaptive system in which the agents constantly react to, influence and are influenced by, the other individuals in the economy. In such systems which are familiar from statistical physics and biology for example, the behaviour of the aggregate cannot be deduced from the behaviour of the average, or "representative" individual. Just as the organised activity of an ants’ nest cannot be understood from the behaviour of a "representative ant" so macroeconomic phenomena should not be assimilated to those associated with the "representative agent". This book provides examples where this can clearly be seen. The examples range from Schelling’s model of segregation, to contributions to public goods, the evolution of buyer seller relations in fish markets, to financial models based on the foraging behaviour of ants. The message of the book is that coordination rather than efficiency is the central problem in economics. How do the myriads of individual choices and decisions come to be coordinated? How does the economy or a market, "self organise" and how does this sometimes result in major upheavals, or to use the phrase from physics, "phase transitions"? The sort of system described in this book is not in equilibrium in the standard sense, it is constantly changing and moving from state to state and its very structure is always being modified. The economy is not a ship sailing on a well-defined trajectory which occasionally gets knocked off course. It is more like the slime described in the book "emergence", constantly reorganising itself so as to slide collectively in directions which are neither understood nor necessarily desired by its components. (shrink)

In economics in situations where there is uncertainty one has to attribute some attitude to handling this uncertainty to individuals. The original idea was to assume that “people do not make systematic mistakes” for which Muth coined the term “rational expectations”. This was replaced by a much more formal vision which suggested that people fully understand how the economy evolves. In this paper I will argue that the foundations of the “rational expectations” hypothesis which has underpinned most recent modern macroeconomic (...) models, which have, in turn, been used for policymaking, are unsound. From a philosophical point of view the idea that agents can not only forecast the evolution of their environment but also their own evolution seems unjustified. If agents do manage to coordinate on specific expectations these may not be rational and can be self fulfilling. From an econometric point of view, when there are changes in the evolution of the economy, it is not rational to satisfy the hypothesis. Furthermore the empirical and experimental evidence suggests that we should abandon this route. (shrink)

Cette communication traite de l'utilisation des concepts évolutionnaires en économie. Une approche a été d'utiliser Vidée de révolution comme une vague analogie. Il y a deux exemples de ce type d'approche. Certains; comme Friedman, ont utilisé la notion de sélection naturelle afin de justifier le modèle standard de la théorie économique, celui d'Arrow-Debreu. D'autres ont utilisé l'idée d'évolution comme base à une critique de la nature fermée et statique de ce modèle. Une autre approche a été de prendre l'idée de (...) l'évolution au sérieux, comme cela a été fait en théorie des jeux évolutionnaires. Je suggère que même dans ce cas, le modèle standard est incompatible avec un point de vue évolutionniste et qu'il ne suffit pas d'utiliser l'évolution comme outil pour sélectionner parmi les équilibres statiques. Des modèles économiques compatibles avec une approche évolutionnaire doivent nécessairement être très différents des modèles standards qu 'on utilise aujourd'hui.This article discusses the use of evolutionary concepts in economic theory. One approach has been to use evolution as a loose analogy. There have been two principle examples of this approach. Those such as Friedman who have used the notion of "natural selection" to justify' the standard model in economic theory, that of Arrow-Debreu and those who have used it to criticize that model for its closed and static nature. A second approach has been to take the idea of evolution more seriously as has been done in evolutionary game theory. I suggest that even in this latter case the standard model is incompatible with a truly evolutionist view and it is not enough to use evolution as a tool to select amongst static equilibria. Economic models which are consistent with an evolutionary approach have necessarily to be very different from the standard ones in use. (shrink)

ABSTRACTThe financial crisis of 2008 was unforeseen partly because the academic theories that underpin policy making do not sufficiently account for uncertainty and complexity or learned and evolved human capabilities for managing them. Mainstream theories of decision making tend to be strongly normative and based on wishfully unrealistic “idealized” modeling. In order to develop theories of actual decision making under uncertainty, we need new methodologies that account for how human actors often manage uncertain situations “well enough.” Some possibly helpful methodologies, (...) drawing on digital science, focus on the role of emotions in determining people's choices; others examine how people construct narratives that enable them to act; still others combine qualitative with quantitative data. (shrink)