STOCK‐FLOW INTERACTIONS,DISEQUILIBRIUM MACROECONOMICS AND THE ROLE OF ECONOMIC POLICY

This paper presents the ‘KMGT’ (Keynes–Metzler–Goodwin–Tobin) portfolio model and studies its stability properties. The approach to macrodynamic modelling taken here extends the KMG model of Chiarella and Flaschel (2000) , focusing in particular on the incorporation of financial markets and policy issues. The original KMG model considered three asset markets (equities, bonds and money) but depicted them in a rudimentary way so that they had little influence on the real side of the model. The only financial market influencing the real side of the economy was the money market (via an LM curve theory of interest). Here Tobin's portfolio choice theory models the demand for each asset in such a way that the total amount of assets that households want to hold equals their net wealth, which is a stock constraint attached to portfolio choice. There is also a flow constraint, that the net amount of assets accumulated (liabilities issued) by one sector must equal its net savings (expenditures). The Tobinian macroeconomic portfolio approach characterizes the potential for financial market instability, focusing on the interconnectedness of all three markets. The paper goes on to study the potential for labour market and fiscal policies to stabilize unstable macroeconomies.