A new statute was recently passed in Wisconsin that transformed the state into right-to-work. Two unions have now challenged this decision, which states that employees within the private-sector covered by union contracts are not required to pay union dues. Three decades ago, 22% of private-sector employees in Wisconsin were union members. Today that number has fallen to 8%.
See "Unions Challenge Wisconsin's New 'Right-To-Work' Law in Court", The New York Times, March 10, 2015