This study estimates the effect of inheriting wealth on inequality and mobility in the wealth distribution. Using new population-wide register data on inheritances in Sweden, we find that inheritances reduce inequality and increase mobility among heirs. Richer heirs indeed inherit larger amounts, but less affluent heirs receive substantially larger inheritances relative to their pre-inheritance wealth than do richer heirs. The Swedish inheritance tax had a small overall impact but appears to have mitigated the equalizing effect of inheritances. We also investigate the potentially confounding role of pre-inheritance gifts and behavioral responses to expectations about future inheritances, but neither of them change the main finding that inheritances reduce wealth inequality.
That is from a new paper by Mikael Elinder, Oscar Erixson, and Daniel Waldenström (pdf), via Ben Southwood.