Here is a TED Talk by Richard Wilkinson who is the co-author of “The Spirit Level – Why More Equal Societies Almost Always Do Better”. The books focuses on how inequality in a country is conducive to unhealthier, unhappier, greater obesity, higher crime rates etc. However critics have said it lacks substantive data – can we say that because New Zealand has a bigger income gap than Greece that it has greater social problems? Richard Wilkinson goes through a lot of the graphs and data that he mentions in the book.