Modéliser les mécanismes sociaux

A lire, ce billet de Daniel Little sur la modélisation des mécanismes sociaux via les agent-based models. Little soulève des questions très importantes :

So here is an interesting question: how do these considerations play into the topic of understanding social outcomes on the basis of an analysis of underlying social mechanisms? Assume we have a theory of organizations that involves a number of lesser institutional mechanisms that affect the behavior of the organization. Is it possible to develop an agent-based model of the organization in which the institutional mechanisms are the units? Are meso-level theories of organizations and institutions amenable to implementation within ABM simulation techniques?

Le problème posé est celui de la modélisation des « objets sociaux » tels que les institutions dans le cadre des ABM. C’est précisément le point que je traite dans ce working paper.

J’y exprime une certaine forme de scepticisme, que je vais toutefois certainement être amené à revoir, suite à un échange la semaine dernière que j’ai eu avec un spécialiste. En attendant, on peut toujours regarder cette présentation sur la question :

A quoi sert l’économie ?

Le titre de ce billet est aussi celui de cet article d’Alan Kirman sur Vox. Il y a quelques très bonnes idées, comme par exemple dans cet extrait :

• We should spend more time insisting on the importance of coordination as the main problem of modern economies rather than efficiency. Our insistence on the latter has diverted attention from the former.

• We should cease to insist on the idea that the aggregation of the choices and actions of individuals who directly interact with each other can be captured by the idea of the aggregate acting as only one of these many individuals. The gap between micro- and macrobehaviour is worrying.

• We should recognise that some of the characteristics of aggregates are caused by aggregation itself. The continuous reaction of the aggregate may be the result of individuals making simple, binary discontinuous choices. For many phenomena, it is much more realistic to think of individuals as having thresholds – which cause them to react – rather than reacting in a smooth, gradual fashion to changes in their environment. Cournot had this idea, it is a pity that we have lost sight of it. Indeed, the aggregate itself may also have thresholds which cause it to react. When enough individuals make a particular choice, the whole of society may then move. When the number of individuals is smaller, there is no such movement. One has only to think of the results of voting.

• All students should be obliged to collect their own data about some economic phenomenon at least once in their career. They will then get a feeling for the importance of institutions and of the interaction between agents and its consequences. Perhaps, best of all, this will restore their enthusiasm for economics

La conclusion est également à méditer. J’en profite pour recommander chaudement le dernier ouvrage de Kirman, Complex Economics, qui développe une analyse des systèmes complexes qui est par ailleurs suggérée dans l’article.