Doesn't the fact that left-of-center parties got more votes play a role? This isn't elite politicians like Bismarck or even Disraeli deciding how much to grant. This is mass politicians trying to assemble winning electoral coalitions...
And there is a certain... bizarreness... in the belief that social provisions became less "generous" after 1973... The average OECD government collected 30% of GDP in taxes in 1965 and spent about 7% of that on the military, leaving government civilian spending at 23% of GDP. The average OECD government collects about 43% of GDP in taxes today, and spends about 3% of that on the military.
There have been important changes in surveillance by the state, in the generational distribution of benefit programs, in economic regulation, and other areas. But the fact that the typical OECD government spent 23% of GDP on domestic programs in 1965 and 40% today should not be forgotten.
Brad DeLong