But there is no evidence that a citizenship question would dramatically impact census participation. The census is not like a telemarketing survey where people have the option of adding their names to a “do not call” list. Everyone is required by law to respond. If a household does not fill out the census form, then census workers visit that household to gather census data. If they still cannot get a household to cooperate, nonrespondents can be fined or prosecuted — though in practice they rarely are. Usually, the Census Bureau instead asks neighbors about the household in order to get as much accurate information as possible. This may add costs to the census, but it is not likely to produce inaccurate data.

Moreover, if asking about citizenship is a deterrent to participation by illegal immigrants, then what about the existing census question that asks whether respondents are “of Hispanic, Latino, or Spanish origin” — the only ethnic group specifically called out? Respondents are required by law to tell the government whether they are of Mexican, Puerto Rican, Cuban or other Hispanic origin, which they are required to list (“print origin, for example, Argentinean, Colombian, Dominican, Nicaraguan, Salvadoran, Spaniard, and so on”). If that does not deter the participation of many illegal immigrants, how would a question on citizenship?