> The researchers, led by Raj Chetty, a professor of economics at Stanford University, analyzed more than 1.4 billion federal tax returns, as well as mortality

> The researchers, led by Raj Chetty, a professor of economics at Stanford University, analyzed more than 1.4 billion federal tax returns, as well as mortality data from the Social Security Administration, from the years 2001 to 2014. In that period, the life expectancy of the richest five per cent of Americans increased by roughly three years. For the poorest five per cent, there was no increase. I find it hard to believe that over a period of 13 years a particular group of Americans lived three years longer on average because they could afford more and better healthcare. That's a very significant jump, and to me it seems more likely to be explained by differences in the composition of the top 5 percent. Did it become more white, more educated, more urban, etc.? Can anyone who read the original paper comment on whether that was explored at all?