I am not sure that INSEE had a very precise vision of the French population at that time, after all, France was mostly a rural country and IT did not appear in French administrations until around thirty years later, in the 1970s. As a former colleague once told me, it is more than likely that the data was "intuited" most of the time (to be clear: completely fabricated).

While I know nothing about the work of René Carmille, from what I was told it's that in most cases it was neighbors who denounced Jews, and you could be denounced even if you were not a Jew, but have some disagreement with someone.

Equally in the same proportion, and sometimes by the same people, Jews and more largely all opponents to Nazis, including English or US plane aviators, were hidden by people (one of my grandmothers did it for Jews).

It was a complicated time, with no clear delineation between "good" and "bad" people.