It has been a banner year for America’s unions. In November 33,000 machinists returned to their stations at Boeing having won a 38% wage increase over four years. Their victory followed a seven-week strike that brought the plane-maker to its knees. A month before, 47,000 dockworkers walked out for three days at some of the country’s busiest ports. Teamsters union members at Amazon warehouses in New York are threatening a strike.