The graph represents the percentage of vehicle registrations of the three most common types of commercial vehicles in the US between 1970 and 2010.
Overall, it is clear that the percentage of the truck is the highest among that. However, in the case of the bus represents the lowest percentage during that period.
First of all, the portion of the truck increased continually so it keeps the head position. While the first two years, in 1970 and 1980, it dropped almost 20 percents, the percentage of the taxi increased and occupied the first position first and last. However, afterthat the taxi percents had change pace, going up and down. Lastly, in the case of the bus, it also had change pace but steadily maintains the lowest percentage.