In Britain, the health gap is growing - in the wealthiest parts of the country, people are living on average more than a decade longer than in the poorest parts.
An academic discipline which tries to work out why this health gap exists has also grown.
It's called social epidemiology. You've probably never heard of it, but the science has influenced governments of both the left and right. So what answers has it thrown up?
The most famous comes from the Whitehall II study of civil servants, led by Sir Michael Marmot, which found that people who are in high-pressure jobs, over which they have low control, are at greater risk of heart disease, because of the stress their lowly position causes.
The idea that how much control you have over your work and life affects your health has generated talk in policy-making circles about the need to empower people.
But the evidence is contested. When economists look at the same data, they see something different.
David Aaronovitch hears the arguments.
Sir Michael Marmot, professor of epidemiology and public health at University College London
Anna Coote, former UK health commissioner
Danny Dorling, professor of human geography at the University of Sheffield
George Davey-Smith, professor of clinical epidemiology at Bristol University
Johan Mackenbach, chair of the department of public health at Erasmus University, Rotterdam
Angus Deaton, professor of economics and international affairs at Princeton University
Producer: Ruth Alexander.