A think piece by Walter Frick at Harvard Business Review (“Understanding the Debate Over Inequality, Skills, and the Rise of the 1%,” Dec. 21) draws a line in the inequality debate between those (mostly CEOs and other corporate apologists) who see it as resulting from a mismatch between the supply and demand for certain skills,…

Now is very different from then. Over the last two hundred or so years, the most dramatic shift in human history since the adoption of agriculture has swept the world, as chemical energy released from coal and oil supplanted human and animal muscle as the primary source of productive power. For the first time since…