The United States purports to have an unusually strong commitment to equal opportunity, yet surprisingly it hasn't collected the mobility data needed to reliably monitor whether that commitment is being upheld. Although mobility and opportunity cannot of course be equated, it's widely understood that mobility data provide fundamental evidence on opportunity, which is why virtually all late industrial countries, save the U.S., have well-developed systems for monitoring mobility. It's not as if the U.S. is a more general laggard in developing social indicators. To the contrary, it has a well-developed program for measuring unemployment and related labor force statistics, a comprehensive set of indicators for monitoring educational outcomes, and an improving system for monitoring poverty and income inequality. The purpose of this project is to provide the first analyses of intergenerational mobility based on U.S. tax returns and to thereby assist in developing mobility indicators that are as reliable, sound, and comprehensive as those available in these other domains.