Final answer:
The situation described is an example of exponential decay, where a quantity decreases by a consistent percentage over equal time intervals.
Step-by-step explanation:
The phenomenon described where the number of people eating at Red Robin decreases by 4% each week is exponential decay. Exponential decay refers to a situation where a quantity decreases by a consistent percentage over equal time intervals. In contrast, exponential growth would imply an increase by a certain percentage over time, which is not the case here.