(M. Spencer Green/Associated Press)

But researchers at Boston College’s Center for Retirement Research believe there’s another explanation. In a new paper, researchers argue that economic boom times create a scarcity of caregivers in nursing homes, raising the mortality rate through a disproportionately high numbers of deaths among the elderly.

The Center for Retirement Research points out that when employment goes up, mortality increases disproportionately among the elderly—who are far less likely to be employed or drive long distances—and among older women, in particular. “Deaths among people ages 65 and older accounted for 75 percent of the 6,700 additional deaths,” the paper points out. “Notably, women over 65 alone accounted for 55 percent of the additional deaths.”