The sweeping racial changes transforming the United States come with an important demographic dimension: age. The waves of Hispanics and Asians and multiracial Americans reshaping the country’s population are full of young people, who by some measures already outnumber their white counterparts. The trend was punctuated by the arrival in 2011 of the ?rst “majority-minority” birth cohort, the ?rst in which the majority of U.S. babies were nonwhite minorities. Consequently, the racial makeup of the nation’s younger population is beginning to contrast sharply with that of baby boomers and seniors.For most of U.S. history, the white population has been viewed as “mainstream” society, with sociologists viewing the assimilation of immigrants and ethnic minorities as dependent on their adoption of its way of life.1 Not coincidentally, whites were the numerically dominant racial group in the United States during that same time. (Between 1790 and 1980, whites ranged from 80 to 90 percent of the population.) But whites’ tenure as America’s mainstream population is on the wane, in a demographic sense.. White children will become a minority of children under age 18 well before 2020, and, soon thereafter, the white population as a whole is projected to begin to decrease.. The 2010 census indicated that the