Taking the newly released UN Human Development Index (HDI) figures from
here, and percentage of unbelief figures from
here (specifically, the Gallup figures), I decided to take a look at how they were related:
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The green curve is a loess curve, which simply smooths the relationship to indicate the basic trend.
The fact that HDI increases with Unbelief percentage does not mean that greater unbelief necessarily
causes greater HDI; the causality may run the other way, or both variables may be caused by some other variable, or there may be complicated feedback between the two variables, and probably several other causal factors (which is what I would imagine is the truth).
The identified countries, clockwise from top left, are United Arab Emirates, USA, Ireland, New Zealand, Australia, Norway, Sweden, Estonia, Azerbaijan, Mongolia, Vietnam, Zimbabwe, Dem.Rep.Congo.