In 1968, biologist Garrett Hardin called this the tragedy of the commons. It happens because each user reasons, "I don't use the resource, someone else will. The little bit I use or pollure is not enough to matter." With few users, this logic works, However, the cumulative effect of many people trying to exploit a common-property resource eventually exhausts or ruins it. Then no one can benefit from it. Therein lies the tragedy.