On the subject of inequality, this TED talk by Richard Wilkinson makes good use of data to show that unequal incomes can have a dramatic negative effect across society.
This chart is at the heart of what he is explaining:
[…] I want to go back though to this graph that I showed you earlier where we put it all together to make two points. One is that, in graph after graph, we find the countries that do worse, whatever the outcome, seem to be the more unequal ones, and the ones that do well seem to be the Nordic countries and Japan. So what we’re looking at is general social disfunction related to inequality. It’s not just one or two things that go wrong, it’s most things.
Much more information can be found on the Equality Trust website.