The three regimes of the IS-LM model: A non-Walrasian analysis

Three different versions of the IS-LM model are generally found in the literature: A first version assumes both price and wage rigid, and excess supply on the two markets. A second version assumes a rigid wage, but a flexible price clearing the goods market. Finally, a third version assumes that both markets are cleared. We develop in this paper a synthetic model which displays the three above cases as particular regimes of the same model, by formalizing the implicit assumption of Keynesian models that the price and wage levels are rigid downwards, but flexible upwards. The resulting non-Walrasian equilibria can be of three types, which correspond to the three versions of the IS-LM model described above. In each case we show how production and employment are determined, and compute the multipliers for fiscal and monetary policy. Finally, the parameter space is partitioned into three subregions corresponding to each regime.