Steelworkers leave a plant at the end of their shift in Bethlehem, Pa. in 1947. Employment in the industry has declined by 80 percent from its peak 6 decades ago, according to author Douglas Irwin.

Steelworkers leave a plant at the end of their shift in Bethlehem, Pa. in 1947. Employment in the industry has declined by 80 percent from its peak 6 decades ago, according to author Douglas Irwin.