Is the Sum of the Individual Preferences the Same as the True Group Preference?

Introduction

The term ‘Tragedy of the Commons’ comes from an article that describes a potential dilemma in which many individuals that act independently and only in their own self-interest can eventually destroy a shared resource, even if it is clear that the livelihood gained from that resource will be jeopardized in the long term.

In this activity, students will act as goat farmers. They will have the ability to decide how many goats they purchase or sell to put on the communal grass area. They will be able to see the health of the grazing area as well as the milk production, their total assets, number of goats and a few other parameters.

Instructions

Since the setup for this activity can be complicated, we recommend that you do a trial run before running it with students. The Hubnet Activity can slow down considerably if there are too many computers logged into it at once. We recommend having no more than 10 computers going at the same time, thus some students may need to double up.

Student Information:

Variables that can be controlled by the students-

·  number of goats they purchase or sell.

What a student can see-

Their own personal information:

·  Goat color

·  Their goat population

·  Current revenue- how much milk they produced for that day.

·  Total assets- based on how much milk they have sold and is automatically calculated.

Information from the system that is affected by other goat farmers:

·  Grass Amount- amount of grass available to eat for all goats

·  Milk Amount- amount of milk produced by all farmers each day


Variables that can be controlled by the teacher-

·  Initial number of goats each farmer has- we suggest that if the group is large that all farmers start with 2 goats. If the group is relatively small (3 or 4 users) the initial number of 5 is fine.

·  Grazing Period- the time frame in which goats are allowed to graze each day

·  Grass Growth Rate- amount of grass growth for each tick of the clock. Increase this variable if your group is larger than 7 players.

·  Cost per goat- amount of money needed to purchase a new goat.

What can be seen on the main computer- (all are measured in days)

·  Milk Supply- amount of milk produced over time

·  Average Revenue- average revenue of all farmers over time

·  Grass Supply- amount of grass available to graze upon over time

·  Goat population- number of goats on grazing field over time

Doing the Activity

Step 1- Teacher opens up Tragedy of the Commons from the models library, hubnet activities. Press the ‘Login’ button

Step 2- students open up their Hubnet Client, found in the Netlogo folder. It is not necessary to start Netlogo, just the Hubnet client. Students will enter their name. Once everyone has logged in turn off the Login by clicking the button again and then hit the Setup button to refresh the screen on everyone’s computer.

Step 3- Teacher adjusts the 4 slider variables accordingly. The defaults should be fine, except if there are more than 7 players, you might want the initial number of goats to be 2 or 3 and increase the growth rate of the grass.

Step 4- 1st Trial

Give very little information to the students. In this first trial, they are to play the game and make observations that can be shared with the rest of the group. Let them know they are going to play a ‘game’ in which they are a goat farmer that has goats in a field shared by other goat farmers. As a goat farmer, they make money by producing milk. As you acquire money (assets) they will be able to purchase more goats or they may decide to sell off some goats. This is determined by moving the slider whenever they want.

Run the activity until you think students are ready for a conversation about it. (5-10 minutes)

Step 5- debrief with the students.

What did they observe? What is happening to the grass? The milk supply? What was their strategy? What information seemed to be the most important? Why?

Refer to the graphs that are on the teacher’s computer and have them analyze what is happening in them.

Step 6- 2nd Trial

This time, students are to maximize the milk amount. They should be able to discuss their strategy when finished with this 2nd round.

Step 7- Debrief with students

What was different this time? How well did the grazing area do compared to the 1st run? In what ways could everyone be kept ‘happy’ including the grazing area?

Step 8- 3rd Trial

If students haven’t already started communicating and strategizing with others about the grazing situation, have them discuss a strategy that would make everyone ‘happy’ and in which they act as a cooperative group. Have them implement the strategy in the 3rd round and be ready to discuss the results and see if it met their individual needs. How do you come to a fair decision in which the economic needs are balanced with the health of the ecosystem?

Step 9- Final Debrief

What did you learn while doing this activity? In your own words, what is meant by ‘Tragedy of the Commons’? What are some of the factors that contribute to this ‘tragedy’ and how can it be avoided?

What are some parameters that are missing in this simulation? (i.e. aging, death, seasons, etc.)

What are the assumptions of this simulation?

Going Further:

If you’d like to extend this activity, you can show students how to export the data of the graphs into a .csv document and then to import that data into Excel with the number of goats on the x axis and the y axis with number of assets. The group or individuals can then analyze these graphs.