The category “Black, African Am., or Negro” was used in Census 2000, based on research in the late 1990’s that showed there was an older cohort of African-Americans who self-identified as “Negro.” Surprisingly, about 56,000 persons took the time to write in under the “some other race” category the word “Negro.” Above half of them were less than 45 years of age in 2000.
The Census Bureau didn’t do any research on the respondent reaction to the word “Negro” in the 2000’s, but did do tests that showed answers to the ethnicity and race questions tended to change depending on the order of the questions. I think some research on the sensitivity of answers to the presence of “Negro” should have been done last decade, but I am unaware of what limitations there were on the research program then.
Some of the commentary on the question comes from people offended by the term. I apologize to them.
Better late than never.