Union Membership as a Percent of Employment Union membership grew dramatically from the mid-1930s until after World War II. Following the war, over one-quarter of American workers were unionized. Union membership has fallen because benefits obtained by unions for union members spread throughout the wider workforce, making the benefits of joining a union less valuable. Also, the changing economy led to faster growth in the service sector, which has traditionally been less unionized.

AP Photo/Kevork Djansezian