Final answer:
The improvement in wage earners' conditions can mainly be attributed to the passage of minimum wage laws. These laws regulated wages and work conditions, which in turn decreased the perceived need for union representation among workers.
Step-by-step explanation:
The condition of a significant segment of adult wage earners improved due to B. the passage of minimum wage laws.
Unions have played an important role in labor history, advocating for improved conditions and fair wages. However, after the enactment of labor laws that mandated minimum wages and regulated work conditions, many workers felt less need for union representation. This is evident in the trend that in high-income economies, such as the United States, union membership decreased since the wages of a larger proportion of the workforce are often regulated by these legal standards, not solely through union negotiations.
Additionally, a myriad of factors, such as globalization, the shift to service industries, and increased social benefits, have led to cultural shifts regarding the perception and necessity of unions.