Productivity growth is really just companies learning how to do more with less; how to bring in more revenue while paying less for inputs. That wage growth kept pace with productivity growth in the middle of the century suggests that workers were sharing in that success — that the additional revenue created by productivity improvements wasn't just hoovered up by shareholders and CEOs, but was distributed out to the workers who made it happen, via higher paychecks.

When wages stopped growing but productivity kept sailing upward, that meant workers weren’t getting their cut anymore. Indeed, inequality started taking off just a few years after the minimum wage stopped rising in real terms and overall wages diverged from productivity.