Final answer:
The decline in labor union membership is attributed to workplace protection laws, which made workers feel less need for unions, the shift from manufacturing to service industries, and globalization.
Step-by-step explanation:
The question asks what has declined alongside the political power of labor unions. The decline in the number of union workers can be attributed to various factors. One significant factor is the sense of reduced necessity for unions due to the enactment of workplace protection laws. Laws concerning work conditions, overtime, parental leave, and pensions, which were once strongly advocated for by unions, have made many workers feel that they no longer need the representation and protection that unions offer.
Other explanations for the decline in union membership include the shift from manufacturing to service industries, the force of globalization, and increased competition from foreign producers. This transition has reshaped the labor market and reduced the influence of unions in the newly dominant service sector. Globalization, in particular, has contributed to the pressure on unions as companies seek to reduce costs and increase profits in a competitive global marketplace.