Between 1980 and 1990, the number of licensed motor carriers increased to over how many?

The correct answer reflects a significant historical trend in the trucking industry. Between 1980 and 1990, the deregulation of the trucking industry led to a substantial increase in the number of licensed motor carriers. This period saw a rise from fewer than 20,000 licensed carriers to over 40,000. The deregulation stimulated competition, which allowed new companies to enter the market, leading to this sharp increase.

This context helps illustrate why over 40,000 is the accurate figure; it showcases the impact of policy changes during that decade on the trucking landscape. Understanding these dynamics is essential for grasping how the trucking industry evolved during that time.