As a part of the decennial census operations, the U.S. Census Bureau creates an address list of housing units in the United States, and mails out census forms to most of those housing units. People who do not mail back their census forms are visited by a census interviewer who comes to record their data during a personal interview. This visit is a part of the Nonresponse Followup (NRFU) operation. Bates and Mulry (2007) studied characteristics of initial non-responders in Census 2000 and found that they were disproportionately economically disadvantaged (characterized by, for example, poverty, public assistance, and unemployment), unattached and/or mobile singles (characterized by, for example, non-spousal households, renters, and residential mobility) and found in high-density areas with ethnic enclaves (characterized by, for example, crowded housing, and less than high school education).