In all cases, in all eras, among all peoples, 1) an homogenous population, 2) markets, 3) rule of law (tort law, not legislation), 4) and the resulting end of corruption generates good conditions.
A diverse population, lack of markets, rule by discretion, generate corruption, and result in bad conditions.
https://www.quora.com/Is-it-U-S-democracy-that-brings-about-a-better-life