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Instructions for the Multi-person Version

Instructions for the Multi-person Version 

These instructions will allow you to simulate the dynamics of the Tragedy of the Commons in your class. To play it requires that all the students can be assembled in a classroom with enough computers with Internet connections to allow all students to be online simultaneously (students can double up if need be). It helps if the instructor’s computer has a projector connected so the results can be easily seen and discussed. The basic elements consists of a game played in several rounds, during each of which all students decide how many cows they will place on the commons. Each student is a farmer who has their own webpage on which they enter the number of cows they wish to graze on the commons for that round. After all students have confirmed that they have submitted their number of cows to the program (and have a "Please Wait" screen), the instructor goes to the instructor’s page (ncowmanage.shtml) and clicks the submit button to tell the program to calculate the results for that round (the program has no way to know when the "round" has ended unless the instructor clicks the submit button). The instructor has the option of revealing the names of the "farmers" by entering the numbers for the rounds for which names should be printed – if no numbers are entered, no names appear; if "1, 3, 5" are entered (after round 5 is complete, presumably), names appear for the results of round 1, 3, and 5 but not for rounds 2 and 4.

THE MOST IMPORTANT INSTRUCTION OF THE GAME IS #7, namely, that the instructor NOT click the submit button on the management page until AFTER each round (including the first round) has been completed but then you MUST click it after all the students have submitted for each round.

  • Example pages of the game once its been played.
  • My lecture notes for when I run the game simulation in my class.  
  • Online video of the Tragedy of the Commons simulations I ran while at Stanford University.
  • Go to the game page.  Class password required.
  • You may want to assign Mildenberger's 2019 article on racism, Hardin, and the ToC. I assign students to give me pros and cons as to whether I should teach the Tragedy of the Commons or not, and always get great feedback.


Running the game requires two URLs, one for students and one for you as the instructor or game manager.

1) Contact Ronald Mitchell at to set up a password and folder which will allow you to play the game.

2) As a homework exercise, have all students go to the main Tragedy of the Commons page and follow the link for the one-person version of the game that shows them how easy it is to optimize use of a private farm. This part is important to make the point that what causes the Tragedy of the Commons is not greediness but whether access is common or private. The students should think about the fact that they are equally "greedy" in both cases but that in the private farm case their "greed" leads them to find the optimal number of cows and then only graze that number for eternity, which they will see is not true in the Commons case. It usually takes people about 8 or 9 tries to optimize milk production in this "game against nature" in which the real analogy is just in trying to figure out the "carrying capacity" of the farm which would be dictated by such factors as rainfall, soil quality, and the size of the farm. To help students understand the difference between the dynamics of a private farm and a commons, you might have them notice that, if they knew the right number of cows to optimize on the farm, there would be no point in playing the game, whereas in the Tragedy of the Commons case they do know the optimal number of cows they should put on after the first round (its in the results and is 20 cows per farmer, regardless of how many farmers there are and whether or not any students decide to abstain from putting cows on the commons – this keeps the game more interesting and forces the students to make harder choices).

3) About a week before you want to run the simulation, get two or three students or colleagues together in the computer lab you plan to use and do a test run of the game to make sure you understand how to use it. It is not a professionally designed computer program which does not catch or notify you of most errors – it just doesn’t work properly. But, if you follow these instructions carefully, it will work fine – its been used by many instructors before. I will give you two passwords – one for use in testing and one for the real class.

4) Assuming the test went fine, bring all your students into one computer lab room. There is not a limit on how many can play, but my experience suggests that having more than 25 students playing at one time tends to overload the server and slow things down. Each student will need his/her own terminal, or you can have students pair up.

5) On the day of the game, have all students return to the main Tragedy of the Commons page  and have them enter the password you were given (usually the instructor’s last name). Filling in the password will direct them to a page where they fill in their name which will create a webpage and game account in their name and they can play the Tragedy of the Commons game.

6) Once play begins, *MAKE SURE* that they follow the instructions on the screens, and wait on the "Please Wait Here" page, or it will prevent the game from working properly.

7) The instructor (NOT the students) manages the game from (replace "password" with the same password the students are using).  Manage the game as follows:

  • Ensure ALL students have submitted their cow number for a round and have gotten to the "Please Wait Here" page,
  • Then, click the submit button on the page at
  • Make absolutely sure NOT to click the submit button before a round is over and NOT before the first round is played (doing so will prevent the game from working).  
  • The submit button will cause the program to tally the results and will automatically refresh students webpages.  Students do not need to click on anything. 
  • As noted, this page allows you to keep names secret (the default) or disclose them. You can use this to encourage students to think about how information on who the "bad guys" are (those who graze more than the 20 per-person optimum) helps (or doesn't help) resolve a Tragedy of the Commons game.

8) Let me reiterate that instructors should "test drive" the game with 2 or 3 students or colleagues to avoid unnecessary errors and embarrassment.

I make this game available as a free public service. I certainly hope and will try to ensure it works but I cannot be responsible for problems or for spending too much time running it. I would, of course, appreciate suggestions for improvements, but cannot promise to respond to requests for them. I hope that you will only make appropriate use of the game, will urge your students to do the same, and give me appropriate credit for writing the game.


Ronald Mitchell