10 years ago I filled out the form, and only answered the question as to number of people in household.
This resulted in a Census worker coming to my home. Again I would only answer number of people in household.
This caused a Census Supervisor of some sort to come to my house who stated "I understand you don't want to answer these questions, but we are going to get this done today."
I remember a number of years ago some morning DJ saying on the air the most common answer on the census was "None of your business". After a form and 2 visits from census takers, I was happy to have contributed to those census stats.