[IkmoIkmo]

> So how effective is that alone? It seems per capita income would be the prevalent factor.

It isn't, alone, in a cherry-picked example. But ceteris paribus it's a explanatory factor.

I mean, one could also use your argument the other way around and question whether income is effective as a factor by itself. Cherry pick some country with similar levels of median wealth and a wildly different murder rate and gun laws. Like say the Netherlands and the US. Doesn't really prove a point, it'd be silly to now claim income isn't an important factor.