In Depth Notes on The Tragedy of the Commons

Definition: The Tragedy of the Commons is a parable that explains why common resources are overutilized and lead to undesirable outcomes for society as a whole.
Originator: Introduced by Garrett Hardin, it illustrates the conflict between individual interests and communal benefits.

Imagery: Picture a pasture that is open to all herdsmen.
Initial Condition: For centuries, the herdsmen keep cattle well below the carrying capacity of the land due to factors like tribal wars, disease, and poaching.
Turning Point: Eventually, when a sustainable state is reached, the commons’ inherent logic leads to overutilization.

Each herdsman prioritizes maximizing personal gain:
- Positive Utility: Gaining additional income by increasing herd size (+1 for each new animal)
- Negative Utility: Shared resources lead to a small fraction of overgrazing cost per herdsman, making them less sensitive to the degradation caused by their actions.
Consequence: Herdsmen add more animals leading to collective ruin as each acts in their own self-interest.

Common Tragedy: Each herdsman, rationally pursuing personal gain, contributes to the depletion of a shared resource, highlighting a tragic irony: freedom in the commons leads to ruin for all.
Mankiw's Example:
- In a small medieval town, families collectively own grazing lands (Town Commons).
- Initially, with ample open land, sheep grazing causes no conflict; however, population growth leads to overcrowding.
- Land quality diminishes, resulting in barren grounds and the collapse of the wool industry with families losing their livelihood.

Difference Between Social and Private Incentives: Individual shepherds do not see their actions as harmful when their individual sheep count seems negligible compared to the collective problem.
Externality: Grazing one family’s flock reduces the available land quality for others, creating a shared burden overlooked by individual decision making.

Regulation: Limit the number of sheep each family can keep.
Economic Measures: Implement taxes on sheep or auction limited grazing permits to internalize the externality.
Historical Solution: Transition from common land to private ownership by subdividing the land, leading to each family managing their own parcel, preventing overgrazing.
- Historical Context: This approach was observed during the enclosure movement in England in the 17th century.

General Lesson: The Tragedy of the Commons demonstrates that individual use of shared resources can diminish others' enjoyment.
Government Role: Effective interventions can include regulations or taxes, or converting common goods into private property to ensure sustainable use.
Philosophical Insight: As Aristotle noted, common resources are often poorly maintained because individuals prioritize their personal property over communal assets.