In a recent article in The American Prospect, Monica Potts examines the mystery of what is killing poor white women. Research on longevity by Jay Olshanky from the University of Illinois in Chicago and a team of collaborators found that white women who dropped out of high school are dying on average five years earlier than the their equivalents in the generation before them. These results have researchers baffled – not since the fall of the Soviet Union, when life expectancy for men dropped by seven years, has there been such a dramatic change in longevity in a single generation.

Most Americans, including high-school dropouts of other races, are gaining life expectancy, just at different speeds. Absent a war, genocide, pandemic, or massive governmental collapse, drops in life expectancy are rare. “If you look at the history of longevity in the United States, there have been no dramatic negative or positive shocks,” Olshansky says. “With the exception of the 1918 influenza pandemic, everything has been relatively steady, slow changes. This is a five-year drop in an 18-year time period. That’s dramatic.”

Numerous researchers are investigating the root causes of this drastic shift. Jennifer Karas Montez from Harvard and Ann Zajacova from the University of Wyoming tested a number of potential factors, including employment, income, and health behaviors like smoking and drinking. White female high school dropouts are less likely than women with a high school education or more to work, and if they do work, it is often low wage, low skill jobs in the service sector. But certainly, many other demographic groups work minimum wage jobs. Indeed, black women who dropped out of high school have seen an increase in their life expectancy over this time.

Although women generally outlive men in the U.S., such a large decline in the average age of death, from almost 79 to a little more than 73, suggests that an increasing number of women are dying in their twenties, thirties, and forties. “We actually don’t know the exact reasons why it’s happened,” Olshansky says. “I wish we did.”