Administrative data can enable a wide variety of new and more accurate statistical work by researchers in academia, government, business, and other organizations. In the United States, no statistical findings are more fundamental for economists and social scientists than those produced by the Census Bureau, including the Decennial estimates of population counts and characteristics. But declining response rates to any kind of survey, not to mention concerns about interference and privacy, have raised serious apprehensions about the accuracy of the upcoming count in 2020. This is an equity issue in addition to a statistical one, since concern is particularly acute about miscounts of historically underrepresented or underprivileged groups.   Funds from this grant support a project by the Massive Data Institute (MDI) at Georgetown to use state-level administrative data to bolster the Decennial Census. MDI will work with various states to identify government sources of administrative data that describe people from across geographic areas and subpopulations; determine how to access the data legally and securely; develop tools to clean and standardize that data; and provide documentation, training, and protocols for use by other states.