The immediate reason the word Negro is on the Census is simple enough: in the 2000 Census, more than 56,000 people wrote in Negro to describe their identity - even though it was already on the form. Some people, it seems, still strongly identify with the term, which used to be a perfectly polite designation. To blindly delete it is to risk incorrectly counting the unknown number of (presumably older) black Americans who identify with the term.
Should the Census Offer 'Negro' as an Identity Option? - Yahoo! News
Should the Census Offer 'Negro' as an Identity Option? - Yahoo! News