This paper first presents information on trends and composition of social expenditure across the OECD. Gross public social expenditure on average across OECD increased from 16% of GDP in 1980 to 21% in 2005, of which public pensions (7% of GDP) and public health expenditure (6% of GDP) are the largest items. This paper then accounts for the effects of the tax system and private social expenditure which leads to a greater similarity in social expenditure-to-GDP ratios across countries and to a reassessment of the magnitude of welfare states. After accounting for the impact of taxation and private benefits, social expenditure (1) amounts to over 30% of GDP at factor cost in Belgium, Germany, and France and (2) ranges within a few percentage points of each other in Austria, Canada, Denmark, Finland, Italy, the Netherlands, Portugal and the United States.