Me, too. And I do that on every idiot form I come across, which mostly means government forms. I've been doing it for years; it drives my wife nuts (she's a real "follow-the-rules" type).
I heartily recommend this to all. Take the statistics out of the statists hands; they just use them to divide We, The People.
My wife didn't really approve of it, but that was because she's interested in genealogy, and the census results can be quite useful to geneologists. Since she had researched her own genealogy, she was able to list every ethnic group she had discovered to be a part of her heritage (hint: it wasn't all African.)