Research suggests that an undercount of ethnic population groups may be present in United States Census Surveys due to classification error. Using data from the American Community Survey (ACS), the article estimates the extent to which an undercount of Hispanics and Hispanic ethnic groups results from variations between individual reports of identity and the official definitions used to measure Hispanic ethnicity by the United States Census Bureau. The findings are analyzed within the context of issues of governmentality and highlight the implications that the presence of an ethnic undercount in population estimates due to classification error presents for public administrators and policymakers. Ultimately the article argues that the official enumeration classifications used by government agencies must take into account changing discourses surrounding ethnic and racial identity in the United States to help promote equitable, effective, and efficient systems of policy and governance.