Then don't look at different countries but at the evolution of inequality in a particular country. The rise of inequality in the US since the 1980's is an indictment of the current system. Here's an animated map showing this evolution:

http://www.washingtonpost.com/blogs/wonkblog/wp/2013/09/19/w...

And this article has a chart illustrating the inverse relationship between inequality and well-being in the US:

http://aeon.co/magazine/living-together/peter-turchin-wealth...