"As a savvy reader, you already know that technological change is why the jobs in manufacturing are drifting away from Youngstown, Ohio. You know that most of the drift goes to other American cities, such as Houston or Chattanooga. You know that Appalachian jobs in coal mining are not coming back, because new techniques have permanently cheapened natural gas. You know that the Trump administration's scapegoat, foreign competition, bears little responsibility for any of this. And when foreign encroachment does happen, you know it's good, not bad, for most Americans.

Still, many reasonable people fret. Isn't technological unemployment a real and serious problem? Non-economists of a quantitative bent fret about what we're going to do when all the jobs go away—when, say, autonomous vehicles replace America's 3.5 million truck drivers.

Even some economists, brilliant ones, think we're in trouble. Robert Gordon of Northwestern suggests it in his recent book The Rise and Fall of American Growth (Princeton University Press). Tyler Cowen of George Mason University does too, in Average Is Over (Dutton). The great if misled John Maynard Keynes believed we would lose jobs from technology. So did the still greater David Ricardo. They were wrong.