I was an enumerator for the recent 2020 census. I can tell you that there is no assurance that the census information is accurate.  I don't know how it worked in 1930, but this year we were told that after repeated attempts to reach someone in a residence failed, we were instructed by our superiors to approach neighbors or a building manager for information.  In several cases, I was able to eventually contact the actual resident and found that the information they gave me was usually different than the information I had received from the neighbor or building manager.  So, in short, just because it says so in the census, doesn't mean its true.
David Schaffer
Vienna, Virginia