New research from the Census Bureau indicates that the citizenship question, if included on the 2020 Census questionnaire, would significantly reduce the self-response rate.

We're awaiting a decision in the case of U.S. Department of Commerce v. State of New York from the Supreme Court, as soon as today. The Insights Association joined an amicus brief in the case in opposition to the citizenship question's addition.

"Self-response" means responses to the decennial without requiring non-response followup.

"Predicting the Effect of Adding a Citizenship Question to the 2020 Census," a working paper soon to be published in Demography, predicted "the effect on self-respones to the entire survey by comparing mail response rates in the 2010 ACS, which included a citizenship question, with those of the 2010 census, which did not have a citizenship question, among households in both surveys."

The study estimated "that the addition of a citizenship question will have an 8.0 percentage point larger effect on self-response rates in households that may have noncitizens relative to those with only U.S. citizens. Assuming that the citizenship question does not affect unit self-response in all-citizen households and applying the 80 percentage point drop to the 28.1% of housing units potentially having at least one noncitizen would predict an overall 2.2 percentage point drop in self-response in the 2020 census, increasing costs and reducing the quality of the population count." The results bolster the outcome of a 2018 Georgetown Universit study.

That 2.2 percent of households (per the Census Bureau study) not self-responding just because of the addition of the citizenship question to the 2020 Census could add at least $110-198 million to the cost of the 2020 Census. The most recent Bureau estimates are that each percent of U.S. households that fail to self-respond will cost $50 million (likely an underestumate), while, in the 2010 Census, each percent cost an average of $90 million.