The bureau conducted an experiment during the 2010 Census in which some questionnaires used what has been the standard of separating questions about race and ethnic origins and others combined them into a single question. Demographers found that the non-response rate for the combined question was about 1 percent while it ranged as high as 5.7 percent for questions about race and ethnicity alone.
The bureau also found Hispanics were highly likely to report themselves as "some other race." That category was intended to be a small residual one but has become the third most popular choice after "white" and "black," with most of those using it Hispanic.
In another experiment, the bureau found responses to questions about race did not drop significantly on questionnaires that did not use the word "negro."
The Census sent experimental questionnaires to 488,604 households in 2010. Respondents were interviewed, and 800 people also participated in focus groups.