The number who have refused over the years has been infinitesimally small. I don't know what it is. I just don't remember anymore, and I apologize. After every census, it was 100 to 150, something of that order. Of those, a careful selection of who will be prosecuted is made by the Department of Justice. Typically, with very few exceptions, those prosecutions were successful--it was never a jail term, never ever--and the resulting fines were in the order of $100, $150, $200, something like that.
On November 16th, 2010. See this statement in context.