I took my mom to a talk a couple of weeks ago offered by the Sheldon Chumir Foundation. Their events are always wonderful and I would encourage evryone to attend at least one!
This event’s guest speak was Richard Wilkinson. His book, The Spirit Level, was the focus of the presentation. Wilkinson also support this foundation: http://www.equalitytrust.org.uk
The gist of the talk was, for developed countries anyway, more equal income means a better society for everyone (rich and poor).
Wilkinson (and his team) took indicators published by organizations like the UN, WHO, ILO etc and compiled them. On every indicator from mental health, to incarceration and teen pregnancy the evidence is clear: the more equal the society, the higher the society rates on every indicator published.
Not surprisingly, Japan and the scandinavian countries are the most equal. The US is the most unequal and Canada is in the middle.
We can dismiss the data but I, for one, believe it to be true. Even without graphs we all know that if your neighbours are more or less like you, there is less envy, more friendship, more help and more trust.