Wage Stagnation Is One Disease With Many Causes

(Bloomberg Opinion) -- One of the most vexing and puzzling problems in the U.S. economy is wage stagnation. There are many proposed culprits -- globalization and foreign competition, the decline of unions, automation, outsourcing and industrial concentration. Plenty of high-quality research is being done to disentangle these causes. But stepping back and looking at the history of wages in the U.S. over the past half-century provides a few clues -- as well as raising some intriguing mysteries.