Now, the United States and many other countries are experiencing a new kind of demographic transition. Instead of additional years of life being realized early in the lifecycle, they are now being realized late in life. At the beginning of the twentieth century, in the United States and other countries at comparable stages of development, most of the additional years of life were realized in youth and working ages; and less than 20 percent was realized after age 65. Now, more than 75 percent of the gains in life expectancy are realized after 65—and that share is approaching 100 percent asymptotically.... The new demographic transition is a longevity transition: How will individuals and societies respond to mortality decline when almost all of the decline will occur late in life?...
That's from "The New Demographic Transition: Most Gains in Life Expectancy Now Realized Late in Life," (PDF) by Karen Eggleston and Victor Fuchs. Via @KarenGrepin.