FILE - In this Feb. 4, 1938 file photo, a crowd of 80,000 to 100,000 unemployed members of the United Auto Workers fill Cadillac Square in Detroit to protest against their unemployment and plea for relief measures. On Thursday, March 28, 2013, Michigan's right-to-work law takes effect, a stunning shift in this symbolic capital of organized labor. The historic change is just the latest sign of turmoil in the union movement that has seen its nationwide membership shrink to its lowest levels since at least the 1930s - a paltry 6.6 percent in the private sector. (AP Photo/File)