The growth in the over-100 population is gob-smacking. In 30 years, Pew reports that the number of U.S. centenarians will quadruple to more than 400,000. To get a sense of what this will mean, picture every resident in Tampa, Fla., being over 100. In 1950, only 2,300 people in the entire country were. Most centenarians today are women and will be in the future but men are also living longer. Men will make up about a third of them in 2054, up from a fifth currently, according to Pew. The rapid growth in the over-100 population is part of a larger trend of an aging nation, which creates three pressing policy concerns. First, all these old people are going to…