In 2012, after fourteen years of reseach, Robert Woodbury (pictured at left) published his findings in the American Political Science Review, and went on to receive four major awards for his work. For decades, political scientists had been attempting to discover the most significant leading indicators of healthy societies. Woodbury found it where nobody had been looking. The title of his paper?

The Missionary Roots of Liberal Democracy  (link to pdf)

Its abstract follows:

This article demonstrates historically and statistically that conversionary Protestants (CPs) heavily influenced the rise and spread of stable democracy around the world. It argues that CPs were a crucial catalyst initiating the development and spread of religious liberty, mass education, mass printing, newspapers, voluntary organizations, and colonial reforms, thereby creating the conditions that made stable democracy more likely. Statistically, the historic prevalence of Protestant missionaries explains about half the variation in democracy in Africa, Asia, Latin America and Oceania and removes the impact of most variables that dominate current statistical research about democracy. The association between Protestant missions and democracy is consistent in different continents and subsamples, and it is robust to more than 50 controls and to instrumental variable analyses.

Protestant Christians? That's the light purple color on that World Religions map!
...perhaps not just a correlation?