Using harmonized household survey data, we analyse long run social mobility in the US, the UK, and Germany and test recent theories of multigenerational persistence of socio-economic status. In this country comparison setting we find evidence against Gregory Clark’s “universal law of social mobility”. In general, our results show that the long run persistence of socio-economic status tends to vary with the institutional context. Our findings on the existence of a direct and independent effect of grandparents’ social status on grandchildren’s status are mixed.