Some of the possible determinants of the changes observed in the welfare caseloads have been analysed in this study. Our model attempts to explain variations in the welfare caseloads on the basis of four different factors: macroeconomic conditions, interactions with other income maintenance programmes, changes in the programme’s parameters and changes in the demographic structure. The model was tested by applying different time series techniques. The data employed is of an administrative nature and covered the whole period the Madrid programme has been in operation. The results show that institutional factors carry more weight than macroeconomic factors concerning changes in the welfare caseloads. The results warn against the standardisation of political decisions given that the effects vary considerably among the different demographic groups.