Humanities · Game Theory
Tragedy of the Commons
A shared pasture. Five farmers. Each wants to add more livestock — but the grass is finite. When everyone maximises their own herd, the common resource collapses. Can you find the strategy that sustains the commons?
The Dilemma
- Individual payoff — each extra animal earns money for the farmer
- Shared cost — overgrazing degrades the pasture for everyone
- Nash Equilibrium — the "rational" choice leads to collective ruin
- Solutions: quotas, taxes, privatisation, or voluntary cooperation
The Shared Pasture
Pasture Health
Your Decision — Each Round, Choose How Many to Graze
You (Farmer 1)
Farmer 2 (AI)
Farmer 3 (AI)
Farmer 4 (AI)
Farmer 5 (AI)
Resource & Wealth Over Time
Green = pasture health · Colored lines = each farmer's cumulative wealth
Garrett Hardin (1968)
Published "The Tragedy of the Commons" — arguing that shared resources are inevitably overexploited without regulation.
Nash Equilibrium
Each farmer's "best response" is to add livestock — even knowing the system will collapse. No individual can improve their outcome by changing alone.
Elinor Ostrom
Won the 2009 Nobel Prize by proving communities can self-govern commons successfully — without privatization or top-down regulation.
Modern Commons
Climate change, ocean fisheries, and internet bandwidth are today's "commons." The same game theory applies at planetary scale.