http://www.slate.com/articles/news_and_politics/politics/2015/09/scott_walker_s_new_labor_plan_the_wisconsin_governor_wants_to_destroy_what.html

As of 2014, 11 percent of all American workers—or 14.6 million people—were in a union. By sector, that’s 6.6 percent unionization for workers in private firms and 35.7 percent unionization for those in government and other public services. Just nine states have unionization rates of 15 percent or greater, down from 28 (and the District of Columbia) in 1984. In whole regions of the country, and the South in particular, unions have nearly vanished. And while as institutions they aren’t powerless—unions still carry clout in the national Democratic Party and have influence in heavily unionized states like New York and New Jersey—they’re also not strong; unions are weaker now than they’ve been in almost a century.