Final answer:
The difference between 1973 and 1980 is 7 years. Without the specific context of the question, it's unclear why one would divide by 8; however, in most cases related to time spans, the beginning year is not counted.
Step-by-step explanation:
The difference between the years 1973 and 1980 is indeed 7 years. If the question concerns calculations related to this period, it's important to consider that we need to analyze the change across these 7 full years. Typically, in calculations involving rates or differences over time, the starting year is not counted in the computation. For example, if we are talking about the number of full years between 1973 and 1980, we would consider the end point of 1980 but not the start point of 1973. That being said, without specific context such as what we are dividing for or why division by 8 might be considered, it's difficult to determine why division by 8 would be appropriate. More context around the data and the type of analysis or calculation being performed might help clarify the situation.