The Hahn Problem refers to the theoretical challenge of building general equilibrium

General equilibrium

General equilibrium theory is a branch of theoretical economics. It seeks to explain the behavior of supply, demand and prices in a whole economy with several or many interacting markets, by seeking to prove that a set of prices exists that will result in an overall equilibrium, hence general...

 models where money does not enter preferences, but yet has a positive value. It is named after the British economist Frank Hahn

Frank Hahn

Frank Horace Hahn is a British economist whose work has focused on general equilibrium theory, monetary theory, Keynesian economics and monetarism...

who outlined this problem in his 1965 paper, "On Some Problems of Proving the Existence of an Equilibrium in a Monetary Economy".