The need to move from descriptive to causal analyses of social change has long been recognized in the social sciences. Due to the difficulties of conducting experimental studies social scientists use comparisons between countries and over time as fruitful strategies to analyze central processes in modern societies. The lack of relevant and reliable data has hitherto constrained comparative research, particularly in the field of social policy where expenditure data often is used. Comparative welfare state research requires more precise indicators on the institutional design of social policies in areas that are crucial for living conditions and capabilities of citizens. This type of institutional information cannot easily be generated from extant data sources. Instead, a considerable amount of basic research is required concerning the organizational setups of welfare states and new institutional indicators must be developed to address key research questions on social policy and welfare states. The purpose of this infrastructural project is to establish the foundations of a new comparative and longitudinal database concerning central welfare state institutions, the Social Policy Indicator Database. The database establishes institutional indicators on national cash benefit legislation and initiates collection of indicators covering also other central areas of the welfare state including social service provision, fiscal systems and tax benefits.