The unique power of incentives are illustrated plainly in a look at the distribution of Western States Endurance Run finishing times. The incentive in this case being the coveted silver or bronze buckle. Runners who complete the course in under a day (24 hours) are awarded the famous silver buckle. Those runners who complete the course within time limits (30 hours) are awarded the bronze buckle.
As evident in the graph below, runners are highly motivated by these buckles with a flurry of runners finishing just at or before the respective buckle cut-offs. The plurality of silver buckle winners finish between 23 and 24 hours, just as the plurality of bronze buckle winners finish between 29 and 30 hours.
