In 1974, New York Times humorist Russell Baker identified a “pig in the python” working its way through the economy: the bulge of 76 million Baby Boomers squeezing through America’s economic system, distorting everything they passed through. When Boomers flooded the labor market in the 1970s, they created a competitive squeeze that never fully released — leaving the generations behind them without the wage rebound economists had predicted. When they bought homes, prices soared. When they took the top jobs in business, culture, and civic life, they held them — and held them, and held them. For half a century,...