Commentary The U.S. economy is suffering from a labor shortage, posing a difficult puzzle for economists and policymakers to solve. The pandemic has deeply disrupted the labor market, with lockdowns causing millions to leave the workforce last year. While many businesses have reopened their doors, bringing back former employees, or hiring new workers, has never been so challenging. And the increasing imposition of vaccine mandates is making the problem worse. Meanwhile, Americans are quitting their current jobs at a record pace. The Labor Department data showed that quits increased to 4.3 million in August, the highest on records dating back to December 2000. Resignations have picked in April this year and remained unusually high during the summer, leading many to call the phenomenon “The Great Resignation” or “The Big Quit.” The number of resignations reached nearly 20 million between April and August this year. Workers at restaurants and stores, especially, are …