The document summarizes research from Wilkinson & Pickett's book "The Spirit Level" showing correlations between income inequality and various social problems. It presents data showing that countries and US states with higher income inequality have worse health and social outcomes, such as lower life expectancy, higher rates of mental illness and drug use, less trust, and poorer child well-being and education. The research suggests these problems are not related to average national income but rather income differences within societies.