Reducing inequality will help make our society more sustainable

A recent report and article in the British Medical Journal by Richard Wilkinson and Kate Pickett highlight the relationship between sustainability and income inequality. They find that happiness and life expectancy are no longer related to wealth. The graphs below from the report show that we have well and truly passed a point of diminishing returns where large increases in wealth have relatively little effect on life expectancy or happiness.
 

However, relative incomes within a society are strongly related to health and wellbeing outcomes (see more graphs from the report below - there are many more examples in the report). They argue that this is related to status differentials rather than material benefits. 

Greater inequality leads to competitive consumerism, as people compete for material displays of status, which in turn leads to much higher greenhouse gas emissions (see graph from the report below).

They conclude that achieving a more equal, sustainable society will require "people's willingness to act for the common good" rather than "private greed, short termism and sectional interests" (p45). We need to focus more on developing social capital; and less on economic growth.