Their book charts the level of health and social problems — as many as they could find reliable figures for — against the level of income inequality in 20 of the world’s richest nations, and in each of the 50 United States.
They allocate a brief chapter to each problem, supplying graphs that display the evidence starkly and unarguably. What they find is that, in states and countries where there is a big gap between the incomes of rich and poor, mental illness, drug and alcohol abuse, obesity and teenage pregnancy are more common, the homicide rate is higher, life expectancy is shorter, and children’s educational performance and literacy scores are worse. The Scandinavian countries and Japan consistently come at the positive end of this spectrum.
They have the smallest differences between higher and lower incomes, and the best record of psycho-social health. The countries with the widest gulf between rich and poor, and the highest incidence of most health and social problems, are Britain, America and Portugal.