Correlation doesn't imply causation. It is plausible that correlation actually goes in the way opposite than what you are >proposing: in wealthier nations people have more disposable money to play zero-sum games with.

Which is why I said predictors, not correlates. There is plenty of research to support my claim; the source I cite points to some of it. Obviously teasing out the arrow of causality is difficult in large scale, trans-generational, international macroeconomic settings, but economists have done their best and the evidence supports the Solow growth model that Metus has brought up.