M&M Game

Hazlett, Denise. "A Common Property Experiment with a Renewable Resource." Economic Inquiry. 35 (October 1997) 858-861.

A series of three classroom experiments demonstrate the tragedy of the commons and suggests two possible solutions: communication and individual property rights. The first experiment consists of the students becoming joint owners of a renewable resource (plate of M&Ms). The plate contains 10 times the number of students in the class—the plate’s carrying capacity. The students privately record the number of M&Ms they want to harvest, with a maximum of 20. Students may not communicate or try to influence each other’s desired harvest. If the total desired harvest is less than or equal to the amount on the plate, the M&Ms are distributed. If the desired harvest is greater, each person gets a probated share [(own desired harvest) x (# of M&Ms on plate / total desired harvest)]. If there are at least eight M&Ms left on the plate, they will reproduce and the game continues. If there are not eight, the population crashes. The second experiment is the same as the first only now the students can now communicate and try to influence each other. In the third experiment, the plate is divided into sections equaling the number of students, and each section has a carrying capacity of 10 M&Ms. Thus, the students have individual property rights to the M&Ms. Each student records the number they wish to consume and reveal simultaneously. If there are at least eight M&Ms on the plate, then each M&M will reproduce itself (remember max. of 10 per portion). If there are not eight M&Ms on the plate total, the population crashes.