Final answer:
The decline in union membership is largely due to a shift from manufacturing to service sector jobs and a U.S. legal environment that is less conducive to union formation and growth.
Step-by-step explanation:
The statement that the growth in small businesses is a reason for the decline in union membership is false. One of the significant explanations for the decline in U.S. union membership involves the shift from manufacturing jobs, where unions were historically strong, to service sector jobs, where union success has been limited. Additionally, the U.S. legal environment is considered less friendly to union formation compared to other countries, which can hinder the ability of unions to organize workers and expand their membership.