The union also found itself challenged by a change in the business climate in the 1970s, as non-union contractors invaded markets that had been solidly union for years with the support of the Business Roundtable, made up of the heads of General Motors, General Electric, Exxon, U.S. Steel, DuPont and others. The Roundtable also attempted to weaken the Davis-Bacon Act and other legislation that protected construction workers. The Iron Workers and other building trades, caught off guard and used to organizing from the top down, lost large amounts of work to non-union contractors in the decades that followed.