Final answer:
Union workers earn approximately 20% more than their nonunion counterparts. Despite this benefit in wages, union membership has declined over past decades, now standing around 11.1% for all U.S. workers and only 6.6% for those in the private sector.
Step-by-step explanation:
Union workers earn 20% higher hourly wages than nonunionized employees in similar positions. This wage premium is maintained even after adjusting for significant factors such as years of work experience and education level. However, it's important to note that there has been a significant decline in union membership over the past decades.
In the mid-1950s, around one-quarter of all U.S. workers were part of a union, while recent figures show that only about 11.1% of U.S. workers are currently union members. When considering the private sector alone, excluding government employees such as public school teachers, the union membership rate drops to 6.6%.