It’s been more than a decade since the Princeton economists Anne Case and Angus Deaton coined the phrase “deaths of despair,” attributing the decline in working class life expectancy in the US, particularly among whites without college degrees, to drug use, alcohol and suicide. But now a new study from Oxford Population Health and the University of Toronto has fingered an entirely different cause of America's life expectancy stagnation: smoking among people without a college degree.

The researchers combed through 33 million death records to figure out how much tobacco use has contributed to the widening gap in mortality among White American adults by education level. The trend lines are stark: life expectancy keeps improving for people with 13+ years of education, stalls for the middle group, and is actually getting worse for those with 11 years of education or less. For a 30-year-old White man in that lower-education bracket, the odds of dying before 80 climbed from 65% to 79% over three decades.

The researchers attributed the growing life expectancy gaps to differing behaviors around smoking. Highly educated Americans have increasingly stopped smoking, while the other groups have continued past, unhealthy, practices. The researchers' own conclusion is blunt: getting more low-education Americans to quit smoking would do more for population health than almost any other single intervention available.

That being said, cigarette smoking may not be the singular problem for long, since as of this year, daily marijuana smoking has become the most common daily drug of choice in the US, surpassing both cigarettes and alcohol.