Even before the sharp and enduring increase in unemployment brought on by the Great Recession, policymakers and researchers were concerned about the “hollowing out” of the U.S. labor market. Over the last 25 years, employment and earnings growth for workers in middle-skill jobs has lagged behind growth for those in jobs requiring both the highest- and lowest-skilled workers. This phenomenon, known as “job polarization,” is most often attributed to new technologies and offshoring of manufacturing processes, which replace middle-skill jobs but complement high-skill jobs.