This chapter provides an overview of different theoretical approaches used to investigate welfare state change with a particular emphasis on cross-national analysis of Western Europe and North America. It distinguishes four families of theories based on the nature of the factors they consider - macro-structures, institutions, actors, individual preferences and attitudes - and the way their influence is conceptualised - as either the environment, filters and interactions, engine or micro-foundations of welfare states. By analysing developments over time, the chapter shows that we have witnessed to both an increased heterogeneity in the ways welfare state change is conceptualised and measured, and a growing integration of theoretical perspectives. In sum, theoretical advancement in this field has occurred less through the falsification and rejection of existing theories than through a process of integration, layering, refinement, and contextualisation whereby new theories have been used to complement and specify older ones and their field of applicability. This development has coincided with a shift away from grand theorising about the state and social conflict to greater emphasis on middle-range theories providing explanation for well-delimited instances of change concerning particular economic forms, periods, sectors or types of reforms.
