The transfer of statistical equilibrium from physics to economics

Two applications of the concept of statistical equilibrium, taken from statistical mechanics, are compared: a simple model of a pure exchange economy, constructed as an alternative to a walrasian exchange equilibrium, and a simple model of an industry, in which statistical equilibrium is used as a complement to the classical long period equilibrium. The postulate of equal probability of all possible microstates is critically re-examined. Equal probabilities are deduced as a steady state of linear and non-linear Markov chains. S. Parrinello wrote the first draft, presented at the “Conference Growth, Unemployment and Distribution: alternative approaches”, (New School for Social Research, New York, March 1995) and published as a Working Paper of the Dipartimento di Economia Pubblica, Università "La Sapienza", Roma (July, 1995). Later T. Fujimoto added section 4 together with Appendix II. Abridged Italian version: S. Parrinello, "Equilibri Statistici e Nuovi Microfondamenti della Macroeconomia", in Incertezza, Moneta, Aspettative ed Equilibrio: saggi in onore di Fausto Vicarelli, a cura di Claudio Gnesutta, Il Mulino, Bologna, 1996.