The impact of increased cost-sharing on utilization of low value services : evidence from the state of Oregon / Jonathan Gruber (MIT and NBER), Johanna Catherine Maclean (Temple University, NBER and IZA), Bill Wright (CORE, Providence Health & Services), Eric Wilkinson (Temple University), Kevin G. Volpp (Corporal Michael J. Crescenz VAMC and University of Pennsylvania) ; IZA, Institute of Labor Economics. Bonn, Germany : IZA Institute of Labor Economics, January 2017