OK, thanks, I managed to find the form they sent me. It was the Census' American Community Survey, which claims "Your Response is Required by Law". I agree that cooperation with the decennial census is required by law to the extent it collects ages and citizenship status of household individuals, but I do not agree that the Census clause of the Constitution authorizes the collection of the American Community Survey information, which is vastly beyond the scope of Congressional districting needs. The claim that my response is required by law is fallacious and is worthy of being challenged in court.
> Could you not answer because you didn't know, or you didn't want to answer those questions?
Didn't know many. Didn't see how the Census clause authorized the collection of personal and private information they were demanding I turn over accurately under criminal penalty otherwise. Not knowing was sufficient to not be able to respond.