The National Labor Relation Act or Wagner Act was passed in 1935 during the tenure of President Roosevelt with the aims of empowering the workers of manufacturing sector mainly. This act covers the workers at lower echelon of the hierarchy and the laborers mainly who have lower bargaining power to negotiate with the management.
The economic structure of the US and the world has completed changed since 1935 when this act was introduced to empower the laborers. The US economy has gone a sea change in structure and size as well as the world economy too has changed significantly. Also the economies of whole world have changed completed in these 75 years. Also the labor market has changed significantly. During this period there have been huge changes in manufacturing sector. The use of technologies has increased and the required workforce is now skilled workforce in the US factories. While this act was introduced this was aimed for unskilled labors. Because of integration of the world market, companies are now outsourcing the production to cheaper markets as the production in the US is very costly and on the employment in those countries is not regulated by the NLRA.
The basic structure and nature of the US economy changed. These factors are having negative impact on labor markets in the US because of restrictive NLRA.