The quality of the decennial census of the United States is compromised by population undercount, which often misses immigrants and racial/ethnic minorities, thereby diminishing federal resources allocated to such groups. Using a modified version of demographic analysis and informed by the latest contributions of emigration scholarship, this research estimates net undercount for the 1990 census relative to the 2000 census by age, sex, year-of-entry, and place-of-birth cohorts. Ordinary least squares estimates suggest that males, recent arrivals, and cohorts aged 15–44 had higher relative net undercount for 1990 compared with 2000. Much higher relative net undercount was found for cohorts from Africa, Latin America, and the Caribbean (excluding Cuba and Puerto Rico) who were ineligible for amnesty under the Immigration Reform and Control Act of 1986 (i.e., those fitting the profile of an undocumented immigrant). Larger implications of these findings suggest that the political climate in which a person is embedded—particularly for persons who may feel threatened or marginalized by the government and/or the public—affects that person’s willingness to respond to the census.