Final answer:
The effect of an event's occurrence in economic terms is referred to as its impact, which can significantly influence supply and demand, and in turn, affect individuals' capacity to provide for their needs.
Step-by-step explanation:
The effect of an event's occurrence is most accurately described as its impact. In economic terms, events can have various effects over which individuals often have very little control. For instance, if a country experiences a natural disaster, goes to war, or faces massive unemployment, these are all economic risks that can dramatically alter the ability of people to provide for themselves and their families. The impact of such an event is the extent to which it affects economic variables like supply and demand. A positive example would be good weather, which is a natural condition that positively affects supply, potentially leading to more abundant crops and lower food prices.