Life expectancy got much higher for most everyone in rich countries over the last several decades. But in the US, the rich are adding years to their life faster than the poor—and probably faster than the rich in other countries.

For example, take a look at the differences between the US and Denmark. A new study looking at life expectancy in both countries shows the lifetimes of high-income Americans grew 140% faster than those of their low-income counterparts from 2001 to 2014. In Denmark, the rich outpaced the poor by less than 20%. The research, conducted by economists at the University of California, San Diego and the University of Copenhagen, also found the situation in Denmark appears to be illustrative of what is happening across many European countries.

Data on incomes and life expectancy is not easy to come by. The US government does not release publicly available data on the finances of people after their death. To estimate the relationship between income and life expectancy, researchers from Opportunity Insights, a policy institute based at Harvard University, gained access to federal income tax and Social Security records. This data, which allows researchers to correlate the historical incomes of Americans to their age at death, is usually kept private to maintain taxpayers privacy. But these researchers were given anonymized data under strict security protocols.

They found men who had reached the age of 40 in 2014 and were in the top 10% in household income could expect to live to 88 years old. For those that were in the bottom 10%, life expectancy was just 76. This means that the richest Americans live 12 years longer than the poorest.

Though both poor and rich people gained years of life since 2001, this 12 year difference was 1.4 years greater than in 2001. The disparities were even greater for women, with those in the top 10% gaining 1.6 more years than those in the bottom 10%.

The researchers attribute the increased variation to differences in smoking and obesity, not access to healthcare. Income inequality also increased over the last several decades, likely exacerbating these differences. Their research was published by the Journal of the American Medical Association in 2016. It is still the most recent data available on the precise relationship between incomes and life expectancy.

Is the extent of US’s life expectancy inequality rise the norm for rich countries? It probably isn’t.

The researchers for the Denmark study used the data from Opportunity Insights for the US, and comparable data on incomes and life expectancy provided by Statistics Denmark. They estimated changes in life expectancy for the bottom, middle, and top third of the income distribution for both countries.

Read the rest of Dan Kopf’s article here at Quartz