The positive correlation between income and democracy that one sees across countries could be due to reverse causation: democracy is more likely to persist as a country grows richer. It could also be due to special historical or cultural circumstances: some societies are just more successful than others, both in terms of economic development and with regard to their ability to develop and maintain democratic political institutions.
我们在一些国家看到的收入与民主之间的正相关性可能是一种因果倒置：民主由于国家日渐富裕而很可能会更稳固。它也有可能是由于特殊的历史或文化环境引起的：在经济发展和发展及维持其民主政体的能力方面，有些社会就是比另一些社会更成功。