An epidemiologist explains the evidence that life expectancy, happiness, and well-being do not increase with income and national wealth.

Question: What is the relationship between economic growth and life expectancy?

Kate Pickett: What we find is, in the rich developed market democracies, there’s no longer any relationship between average levels of income in a country and life expectancy. So, you can have a country like the USA, or Norway, that’s twice a rich as another country like Greece for instance, and that doesn’t seem to affect life expectancy at all. And the same is true of happiness. Happiness isn’t related to average levels of income in a country either. Now, that’s not true of the developing world when you don’t have enough, when people are lacking food or shelter, or the basic material necessities. Then economic growth is really important. But in our rich, developed democracies, it no longer makes any difference. So, we seem to have come to an end of what economic growth can do for us in terms of life expectancy, happiness, well-being and that sort of thing.

If you look at the United States, over the past few decades, you’ve become twice, three times a rich as you used to be, levels of happiness haven’t improved at all.

Question: How does social inequality affect our health?

Kate Pickett: I think this is where it helps that Richard Wilkinson, my co-author and I, we’re epidemiologists, and so we study levels of population health. And one thing we really learned over the past 30 years in epidemiology is the importance of psycho-social factors for health. Things like low social status, or social affiliation, social networks, whether or not you have friends, and the stresses of early childhood. All of those things have turned out to be really important for health. And we have quite a good understanding now of the biology of chronic stress. So, all of these things are working as stresses, low social status, lack of friends or social networks, stress in early childhood. And chronic stress affects our biology, our physiology in lots of different ways. It affects our immune system, our hormonal responses, it affects our cardiovascular health. And that’s quite well understood. And so we have also known for a long time that the people at the bottom of society, the poorer people in our societies, people living in the most deprived neighborhoods have much higher levels of stress and much worse health than those who are more affluent or have higher social status.

Question: Is there a threshold for when economic growth stops affecting life expectancy?

Kate Pickett: Yeah, it’s not so much about the threshold, the threshold changes over time. It’s really just seeing that although life expectancy continues to improve over time, that’s not related to average levels of income anymore in the rich countries. Instead, what we find is really important is the level of income and equality that is the gap between the rich and the poor. That’s what seems to matter these days for our health and social well being.