It would be pretty easy to validate the model, I think: take Eastern Europe, South Korea, Norway, Ireland as examples of countries where the economic growth since 1980 was very obvious, and most of it corresponded to a democratic society. Then take the US, Japan, Germany, France, UK, Sweden as a control group, which was already pretty developed by 1980, and check their trends in light pollution vs GDP, or whatever.

(1980 is an arbitrary date, but before the fall of the USSR and thus the explosive growth of the Eastern Europe, and when shots from orbit likely became easy to obtain.)