One of the most disquieting facts about life in the United States today is that the richest American men live 15 years longer than the poorest men, while for women it’s 10 years. Put a different way, the life expectancy gap between rich and poor in the U.S. is wider than the gap between the average American and the average Yemeni or Ethiopian.

This gap is only getting wider. According to a report by the Health Inequality Project, from 2001-2014, the richest Americans gained approximately three years in life expectancy while the poorest Americans experienced no gains. A three-year difference in life expectancy may seem trivial, but, as the report’s authors note, this gain in lifespan is the equivalent of curing cancer for only the rich. Going back further, the numbers only get worse: The richest American males gained six years in life expectancy from 1980 to 2010, while outcomes for the poorest men remained stagnant.

These facts would seem to justify the Democratic Party’s widespread support for universal health care. Presidential candidates including Bernie Sanders, Elizabeth Warren, Cory Booker, Kamala Harris, and Julian Castro support some form of Medicare for All, and many of the candidates who haven’t fully endorsed MFA have gone to all lengths to convince voters—sometimes unconvincingly—that their plans will guarantee low-cost universal coverage.

When it comes to the health-wealth gap, though, Medicare for All may not be the silver bullet that progressives hope for. Most evidence suggests that while universal health care is a necessary step to closing this gap, it is nowhere near enough. That’s because there are two other major factors that cause the rich to live so much longer than the poor.

If the health-wealth gap is merely the product of access to quality health care, then the gap should largely disappear when health care access is equalized across society. But that’s not the case in countries that already have universal health care coverage. In France, which has one of the best and most extensive health care systems in the world, the health-wealth gap is about 11 years. Even in the United Kingdom, home to the most robust single payer health care system on the planet, the rich live about 9 years longer than the poor.