🌊 What Are Common Pool Resources?
Definition: Common pool resources (CPRs).
Two defining characteristics
- Rivalrous — if one fisher catches a fish, it's gone for everyone else.
- Non-excludable — you can't easily stop boats entering the open ocean.
Examples of CPRs: Ocean fisheries, tropical rainforests, groundwater aquifers, clean air, grazing land.
Why the market fails
Because nobody owns the resource and access is open, each individual has an incentive to use as much as possible before others do. This leads to over-exploitation — a negative externality where individual users don't bear the full cost of depleting the resource.
😱 Tragedy of the Commons
Core concept: The tragedy of the commons explains why CPRs tend to be over-used and degraded.
The logic
- Each user gains the full private benefit of an extra unit of the resource (e.g. one more fish caught).
- But the cost of depletion is shared across all users.
- So the private benefit > private cost of taking one more unit → rational to keep taking.
- When everyone does this, the resource collapses (e.g. fisheries collapse, deforestation).
Classic example: Atlantic cod fisheries off Newfoundland collapsed in 1992 after decades of over-fishing. The Canadian government imposed a moratorium — but the stocks have still not fully recovered 30+ years later.
Diagram link
The diagram is the same as a negative externality of production: MSC > MPC because each user imposes a cost on others by depleting the shared resource. The market outcome (Qm) exceeds the socially optimal output (Qopt), creating a welfare loss.
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🔧 Solutions to the Tragedy of the Commons
The central challenge is to make users internalise the cost of depletion. There are several approaches:
- Government regulation — quotas (e.g. fishing quotas limiting total catch), bans during breeding seasons, protected areas.
- Property rights — if someone owns the resource, they have an incentive to manage it sustainably. E.g. privatising fishing zones gives owners a long-term stake.
- Tradable permits — cap the total use and let users trade permits (similar to carbon markets).
- Community management — local communities can self-organise rules (Elinor Ostrom's research showed this can work when communities are small and have clear boundaries).
- International agreements — for global CPRs like the atmosphere or oceans, international treaties are needed (e.g. Paris Climate Agreement).
Elinor Ostrom won the Nobel Prize in Economics (2009) for showing that communities can manage CPRs effectively without privatisation or government control — but it requires clear rules, monitoring, and sanctions.
Evaluation of solutions
- Regulation can be hard to enforce (e.g. illegal fishing in international waters).
- Property rights don't always work (how do you privatise the atmosphere?).
- International agreements suffer from free-rider problems — countries may not comply.
- Community management works best at local scale; less effective for large, dispersed resources.