While much attention has focused on health disparities between socio-economic groups, most health inequality actually occurs within socio-economic groups. We examine trends in overall health inequality – measured by realized length-of-life inequality – through the lens of social justice, similar to traditional analysis of income inequality. We find that throughout most of the length-of-life distribution, inequality has declined dramatically over the past century. It has continued to decline even in the past 40 years, a period over which it is generally thought that income inequality has risen considerably. Most of the decline in length-of-life inequality appears to be driven by reductions in inequality within socio-economic groups. Using a reasonable estimate of the value of a quality-adjusted life year (QALY) we find that, on a lifetime basis, the least healthy individuals in society have gained more than eight times as much as the healthiest. In dollar terms, the relative gain for the 10th percentile of health relative to the 90th percentile of health is more than $400,000.