The generation is really two groups, estranged from each other by culture and economics. "To go with the Pew Research Center's definition of millennials (those born between 1981 and 1996), the rough midway point of 1988 is a serviceable faultline. We who were born before it are really junior members of Generation X. Those who came after have more in common with Generation Z." Janan Ganesh reflects for the Financial Times.