Discussion papers

CPM-03-114 - 1 April 2003

Re-implementing John Duffy’s model of speculative learning agents in a small scale society: Problems, interest and issues

Juliette Rouchier

Presented at the “Model to Model” workshop, 31st March/1st April 2003, Marseille.


The paper presents an attempt at replication of a multi-agent model dealing with the issue of speculation. In the Journal of Economic Dynamics and Control, John Duffy presents his model and results, as a coupling between an experimental economic version and a multi-agent version, of a model by Kiyotaki and Wright (1989). This original model offers a structural setting on which to base a microeconomic view of speculation, by designing a production-exchange-consumption setting with three goods that differ by their storage costs. Here, I present my own version of the multi-agent model, which is as close as possible to John Duffy’s, although I have been unable to reproduce his actual results. Most of my results are neither close to the experimental data or the simulation data, which makes me discuss the model of rationality of agents itself, and the way the results were described. The replication process is all the more interesting that it allows to redefine the relevant indicators to analyze the model.