The paper proposes a quantitative assessment of the impact of demand-side factors, i.e. growth, composition and distribution of income, in the determination of changes in the aggregate balance of employment. The level of employment “justified” in an economic system is here derived from the application of a simple model which we have called, following the seminal contribution of R. Kahn in 1931, the “Employment Multiplier”. Starting from an accounting identity between values of aggregate supply and demand, the level of “justified” employment is derived, given the labour coefficients and deflated values of the final demand, in which “autonomous” components are distinguished from an “induced” component, this latter depending on total labour income. The variations, over the decades and the cycles, of aggregate employment for Italy, starting from 1960, are then analysed and decomposed into effects of the “contributions” of three components: growth of productivity, of “autonomous” demand and of the “multiplier”, a term which summarizes the impact of trends of employment, real wages and consumption propensity on induced demand.