The short answer is that income is a significant factor but it's complicated. The difference in life expectancy at 50 between the lowest and highest income quin

The short answer is that income is a significant factor but it's complicated. The difference in life expectancy at 50 between the lowest and highest income quintiles is about 13 years in the US [0] vs. e.g. 8 in Denmark [1]. (Other European countries seem to be qualitatively similar to Denmark but I couldn't immediately find another apples-to-apples study to compare.) This gap has widened over time in the US, and in fact life expectancy for the bottom quintile has stayed flat or decreased, despite plummeting tobacco usage and general mortality improvement among black Americans. However, it seems like this is mostly driven by differences in behavior (smoking and obesity rates in particular), not by factors like access to medical care [2], though in general the effect is very heterogeneous. [0] https://fas.org/sgp/crs/misc/R44846.pdf https://fas.org/sgp/crs/misc/R44846.pdf, e.g. Figure 4 on page 14 [1] https://jech.bmj.com/content/75/2/145 https://jech.bmj.com/content/75/2/145 [2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4866586/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4866586/, e.g. Figure 8