LOS ANGELES -- Across the United States, people are living longer than ever. But there's one group that's dying a lot quicker, and nobody knows why. As Monica Potts details in a fascinating piece for the American Prospect, the life expectancy of white women who don't graduate high school has "declined dramatically over the past 18 years." White men who drop out of high school have lost three years in that time period. Women have lost five. They used to live to an average of 79, but now they die around 73. And despite the persistent life expectancy gap between black and white Americans, black women who drop out are living longer than ever -- now, even longer than white women do.Potts speaks with a cluster of researchers who are trying to tease out the variables contributing to the earlier deaths of these female dropouts, but finds no firm answers. It could be that "staying in school teaches people to delay gratification," but that calculus hasn't changed in the past two decades. White women are more likely than black women to "smoke and drink and abuse prescription drugs like OxyContin and street drugs like meth," but it's unclear why that's the case.