Kevin, Rajiv, and Yakov are hunters who live next to a recreational wildlife game area that is open to hunting; in other words, anyone is free to use the recreational wildlife game area for hunting. Assume that these men are the only three hunters who hunt in this recreational wildlife game area and that the recreational wildlife game area is large enough for all three hunters to hunt intensively at the same time.

Each year, the hunters choose independently how often to hunt; specifically, they choose whether to hunt intensively (that is, to set several traps and hunt long hours, which hurts the sustainability of the recreational wildlife game area if enough people do it) or to hunt nonintensively (which does not hurt the sustainability of the recreational wildlife game area). None of them has the ability to control how much the others hunt, and each hunter cares only about his own profitability and not the state of the recreational wildlife game area.

Assume that as long as no more than one hunter hunts intensively, there are enough animals to restock the recreational wildlife game area. However, if two or more hunt intensively, the recreational wildlife game area will become useless in the future. Of course, hunting intensively earns a hunter more money and greater profit because he can sell more animals.

The recreational wildlife game area is an example of because the animals in the recreational wildlife game area are and .