The employment shift from occupations that require mid-level skills toward those at the high and low ends is one of the most important trends in the U.S. labor market over the past 30 years. Previous research has suggested that a primary driver of this job polarization is something called routine-biased technological change (RBTC), an unfortunate mouthful whereby new technologies substitute for repetitive, middle-skill jobs and complement analytical, high-skill jobs. Think of word processors replacing typists or engineers using AutoCAD software. Until recently, economists thought of this trend as a gradual phenomenon that didn’t depend much on the ups and downs of the economy.