Public Goods, Free Rider
The Public Goods Trap
The Public Goods Trap is a Public Goods and Free Rider scenario. The core lesson: Cooperation collapses as the group grows, unless you can punish free riders. Ten strangers each receive $10. You can secretly contribute any amount to a shared pot. DecisionPlay maps the players, payoffs, and equilibrium dynamics that shape how this situation typically resolves.
The situation
Ten strangers each receive $10. You can secretly contribute any amount to a shared pot. The pot is doubled and split equally among all ten, regardless of how much each contributed.
Background
Public goods games are the economic model behind every collective action problem: taxes, open-source software, team effort, climate agreements. The math always favors free-riding: you get 1/10th of whatever you put in, so if you contribute $10 and no one else does, you receive only $2 back, a $8 loss. The dominant strategy is to contribute nothing and let others fund the pot. But if everyone thinks this way, the pot stays empty and everyone gets nothing.
What this reveals
Conditional cooperation
Most people aren't purely selfish or purely altruistic, they cooperate when they believe others are cooperating too. This conditional logic makes cooperation fragile: a few visible defectors can collapse a cooperative group.
How to counter it: In any group you care about, free-riding must be visible and there must be costs for it. Not because people are bad, because invisible free-riding creates rational defection for everyone else.
A question to sit with
In a group you belong to, who is currently free-riding? What happens if nobody names it and imposes a cost on it?
Frequently asked questions
- What game theory concept does The Public Goods Trap illustrate?
- The Public Goods Trap illustrates Public Goods, Free Rider. Cooperation collapses as the group grows, unless you can punish free riders.
- What is the situation in The Public Goods Trap?
- Ten strangers each receive $10. You can secretly contribute any amount to a shared pot. The pot is doubled and split equally among all ten, regardless of how much each contributed.
- What does The Public Goods Trap reveal about how people decide?
- Conditional cooperation. Most people aren't purely selfish or purely altruistic, they cooperate when they believe others are cooperating too. This conditional logic makes cooperation fragile: a few visible defectors can collapse a cooperative group.
- How do you avoid the trap in The Public Goods Trap?
- In any group you care about, free-riding must be visible and there must be costs for it. Not because people are bad, because invisible free-riding creates rational defection for everyone else.
- What is the research behind The Public Goods Trap?
- Public goods games are the economic model behind every collective action problem: taxes, open-source software, team effort, climate agreements. The math always favors free-riding: you get 1/10th of whatever you put in, so if you contribute $10 and no one else does, you receive only $2 back, a $8 loss. The dominant strategy is to contribute nothing and let others fund the pot.
- How long does The Public Goods Trap take to play?
- About 9 min, at core difficulty, across 4 decision points. It runs in your browser with no account and no sign-in.
Keep exploring
More Classical Game Theory scenarios, or browse all scenarios. New to this? Start with how DecisionPlay works or the game theory glossary.
Topics: public-goods, free-rider, cooperation, punishment