Based on a derivation of the asymptotic sampling distribution of the generalized entropy mobility measures, this paper provides a statistically rigorous analysis of income mobility in Germany and the United States using the panel data set PSID-SOEP equivalent data file. Several alternative measures of income aggregation, inequality measures, and groupings are considered to establish robustness. We find that, to a high degree of statistical confidence, post-government income mobility is much higher in Germany. Possible reasons for these findings are revealed through disaggregation of the samples by population subgroups.