In the USA, the Constitution requires a Census every ten years. Anyone living here, legally or not, are required by law to respond to the Census, as well as be truthful. This has been the case from from the first Census taken in 1790, till that last one in 2020.
The punishment has even been amended by Congress twice since its inception.
However, in the last 233 years, only a handful of people have been prosecuted for violating this law. And of those, only two people have been convicted. Of those two, one had the conviction overturned.
What is the point of one of the oldest laws, in which some people have cared enough to amend, but not enough to actually enforce?
This might be more of a political question, but maybe there is a legal reason?
Edit: I cant find exact numbers - and exact numbers might be impossible to get - but from some quick research, it sounds like not answering the census at all is fairly common. From one post on the Census Bureau's website, the answer rate is over 60%. And as far as I can tell, there is no numbers on people responding being complete or truthful.