This report is one in a series that compares data from the American Community Survey (ACS) with data from the Annual Social and Economic Supplement (ASEC) to the Current Population Survey (CPS). The report focuses on comparisons of national distributions of citizenship status, year of entry, and place of birth between the 2004 ACS and the 2004 ASEC. It suggests possible explanations for those differences that are both statistically and substantively different. The population living in group quarters is excluded from the analysis.