Article I Section 2 of the U.S. Constitution describes the House of Representatives and how members are chosen, and it says this about a census:
"The actual Enumeration shall be made within three Years after the first Meeting of the Congress of the United States, and within every subsequent Term of ten Years, in such Manner as they shall by Law direct.." -- Article I, Section 2 of the Constitution of the United States. Link.
Basically it's asking for a head count to determine the number of members the House of Representatives should have. However, the census form that we are all asked to fill out requests much more information than just a head count. So are we required to answer all those questions?
There are those weaselly words in that article in the Constitution: "in such manner as they shall by law direct." And wouldn't you know, our lawmakers wrote some laws with even more weaselly words. See 13 U.S.C. § 141(a): "In connection with any such census, the Secretary is authorized to obtain such other census information as necessary."
And 13 U.S.C. § 221 addresses refusal or neglect to answer questions and false answers. The fine for refusing or neglecting to answer can be up to $100, and the fine for lying on the form can be as high as $500.
The government has the law on its side, so the question is whether to comply or defy.
Those in the "comply" camp might take comfort in 13 U.S.C. § 214 which makes it illegal for the census employees to divulge your personal information. However, we hear all too often about some personal information escaping through misplaced or stolen government laptops, and the threat of cyber-attacks is all over the news these days. So the information is only as secure as the government is able to make it secure.
Some people opine that we don't have to answer all those questions because it seems to go beyond the requirement set out in the Constitution. For example, esteemed George Mason University professor Walter E. Williams says "Unless a census taker can show me a constitutional requirement, the only information I plan to give are the number and names of the people in my household." I would like to think a person could take one step back from that and provide only the number of people in the house with no names.
Here's a little bit of useful info for those in the "defy" camp, or like Professor Williams, have one foot in the "comply" camp and one foot in the "defy" camp. 13 U.S.C. Sec. § 241 says that "registered or certified mail or telegram, the return receipt therefor or other written receipt thereof shall be prima facie evidence of an official request in any prosecution under such section." So if your notice came through regular mail then they would have to prove that you actually got it before a fine would be upheld. On the other hand, if a notice comes by registered or certified mail, they may be getting ready to assess a fine.
Disclaimer: This is a blogger rant containing some cites to relevant statutes, but it isn't legal advice. There is safety in numbers, I suppose, but anyone taking the "defy" route will be taking the risk that the government will throw a fine at them.