A rise in inequality has been proven to generate a “social dysfunction” so powerful it leads to higher levels of mental illness, worse physical health, more obesity, and increased violence.

Question: What is the link between greater inequality and public health?

Kate Pickett: We look at more and less equal countries, and let me describe what I mean by that. We use income equality as a measure of how hierarchical a society is, how unequal it is. And so we’re comparing – we’re looking at countries and looking at how much richer the top 20% of the population are compared to the bottom 20%. It’s ratio of the top fifth to the bottom fifth of incomes. And in more equal countries like Japan, Sweden, Denmark, Finland, the top 20% earn about 3 ½ to 4 times as much as the bottom 20%. And in the more unequal countries like the UK, where I’m from, the USA, Portugal, Australia, Singapore, it’s 7 ½ to 9 times as much. So, that’s the scale of inequality that we’re looking at.

And what we do in our book is take that scale of income differences and look to see how it affect a range of health and social problems in different societies. And we find that more unequal societies have lower levels of trust, higher levels of mental illness, worse physical health, more obesity, their children do less well in schools, there are more teenage births, more violence, as you just mentioned, a greater percentage of the population is in prison and social mobility is lower as well. So, everything seems to get worse in more unequal societies. This is a general social dysfunction. And because this is politically quite sensitive, we thought we’d test it all out again in separate setting. So, we compared the 50 states of the USA as a sort of independent test, and again, we look at levels of income and equality in the 50 different states and compare that tot heir level of health and social problems. And it’s a remarkably consistent picture. So that all those health and social problems are worse in the more unequal states.

And we think this human sensitivity to social relationships is the underpinning cause of all of those problems. You asked about violence, and in a more unequal society, of course, there are more people who don’t have access to the kinds of things that give us status, money, jobs, cars, employment, those sorts of things. And in a society where social judgments can be harsher, those at the bottom are going to be much more sensitive to threats to their status. And we know from the work of prison psychiatrists, for instance, that being disrespected, or humiliated, or potentially losing face is the most common trigger for violence of all. So, I think that’s the link between greater inequality and high levels of violence.

And the differences are huge. If we compare, for instance, the American states and Canadian Provinces, in the more equal of those, there are about 15 million, sorry, 15 murders per million residents per year. And in the more unequal, it’s about 150. So that’s a ten-fold difference, ten times the murder rate in the more unequal places than the more equal ones.