Culturally, the age of inequality is still churning: Over just the last six months, we’ve had the song “Rich Men North of Richmond” and Shawn Fain’s leading the United Auto Workers into a triumphant labor war with Detroit’s Big Three while wearing an “Eat the Rich” T-shirt. But at the structural level, our picture of American inequality also seems to be changing. According to some measures, U.S. income inequality hasn’t meaningfully grown over the last decade, the very period in which it has become such a potent cultural and political…