A piece of the Affordable Care Act called the Cadillac tax has put pressure on municipal unions to accept cheaper health benefits. Upon the advice of economists, the tax was added to the ACA on the basis that the cost of healthcare is inflated when individuals do not have to bear the cost. Employees in municipal unions who often accept smaller wage increases in exchange for more inclusive healthcare coverage will be most affected by the tax. Plans that exceed stipulated levels will be taxed starting in 2018.
See "Health care law raises pressure on public unions", Kate Taylor, The New York Times, August 4, 2013