As population grows, so does regulation.
The correlation suggests to me that regulatory governance has an irrational basis — that is, the need for regulatory control arises from within itself, not as a response to external conditions.
The opposite might be true, of course. Perhaps the volume of problems to be solved expands with the size of a population. That at least would account for the emergence of regulatory governance, although not necessarily for the observed correlation.
Another possibility is that culture is the primary regulatory mechanism in society. Thus, as the population grows its culture weakens, to be replaced with regulatory governance.
Whatever the root cause, the correlation itself seems a handy rule of thumb.