<i><a href="https://en.wikipedia.org/wiki/The_Spirit_Level_(book)" class="extiw" title="en:The Spirit Level (book)">The Spirit Level: Why More Equal Societies Almost Always Do Better</a></i>.
Richard G. Wilkinson &amp; Kate Pickett, Penguin 2009.
Attribution
<a rel="nofollow" class="external free" href="http://www.equalitytrust.org.uk/resources/spirit-level-slides">http://www.equalitytrust.org.uk/resources/spirit-level-slides</a>