Answer:
Treaties have become more common in recent years due to the creation of the United Nations.
Step-by-step explanation:
A hypothesis is a proposed explanation for a phenomenon. These are usually based on previous observations, and are considered a starting point for new theories.
If we look at the treaty activity from the 1960s to the 1990s, we see that treaties among different countries have become a lot more common than they were in the past. A possible explanation for this is the fact that most treaties are now registered with the United Nations in order for them to be used in international law.