The American Community Survey (ACS) includes a write-in question asking for “year of naturalization” for all individuals reported as foreign born and naturalized citizens. However, not all of the foreign born who are naturalized provide the year they became citizens. This paper uses logistic regression analysis and data from the 2011 ACS to determine the characteristics associated with those naturalized citizens for whom year of naturalization is – and is not – reported. The research literature demonstrates that various demographic and social characteristics influence reporting behavior. However, this analysis focuses on two variables: 1) survey environment and 2) social proximity to the respondent. Naturalized citizens in households that provide information about their members using a mail-back questionnaire were more likely to have a reported year of naturalization than those in households interviewed by phone or in-person. In addition, they were more likely to have a reported year of naturalization if they were householders (who usually act as primary respondent) or were closely related to householders. The results of the analysis suggest that item nonresponse is likely to be higher for individuals in complex households with weak ties to the householder and little or no direct contact with the survey instrument or interviewer.