A flow model of the Dutch labour market is used to calculate the efects of autonomouslabour demand and supply shocks on employment and unemployment. The model is centered around a matching function which allows for heterogeneousunemployment by taking explicitly account of POWS through various duration classes of unemployment. The model describes the interaction between flows of jobs and flows of persons, and is based on times series data with respect to these flows at the macro level. A positive labour supply shock,representing a policy which aims at enhancing labour participation, appears to lead to more employment indeed, but the eflect is rather small in case of the present situation in The Netherlands with much more unemployment than vacancies. A sensitivity analysis shows to what extent the effects of laboursupply and demand shocks depend upon the pace of labour market dynamics and on the relative position of the reduced form W-curve implied by the model.