This is sometimes known as the Laffer Curve, and this common-sense theory is explained in the following video.

FORBES: Understanding the Laffer Curve

But cheating to get ahead at any cost (particularly at the cost of another classmate if, for example, a test is graded on a curve) and collaborating with classmates for the common good are different ethical animals.

FORBES: Is Teaching Collaboration The Catch-22 Of Education?

Since small deviations are common and large ones are rare, the result of plotting data in this way is a curve shaped somewhat like the cross-section of a bell.

ECONOMIST: Climate change