This volume offers a synthesis of what is known about very large and very small common-pool resources. Individuals using commons at the global or local level may find themselves in a similar situation. At an international level, states cannot appeal to authoritative hierarchies to enforce agreements they make to cooperate with one another. In some small-scale settings, participants may be just as helpless in calling on distant public officials to monitor and enforce their agreements. Scholars have independently discovered self-organizing regimes which rely on implicit or explicit principles, norms, rules and procedures rather than the command and control of a central authority.

The contributors discuss the possibilities and dangers of scaling up and scaling down. They explore the impact of the number of actors and the degree of heterogeneity among actors on the likelihood of cooperative behaviour.

Introduction - Robert O Keohane and Elinor Ostrom
PART ONE: THEORETICAL PUZZLES
The Problem of Scale in Human/Environment Relationships - Oran R Young
The Politics of Scope - Duncan Snidal
Endogenous Actors, Heterogeneity and Institutions
Heterogeneity, Linkage and Commons Problems - Lisa L Martin
PART TWO: EVIDENCE FROM THE LABORATORY
Heterogeneities, Information and Conflict Resolution - Steven Hackett, Dean Dudley and James Walker
Experimental Evidence on Sharing Contracts
PART THREE: EVIDENCE FROM THE FIELD
Constituting Social Capital and Collective Action - Elinor Ostrom
The Conditions for Successful Collective Action - Gary D Libecap
Self-interest and Environmental Management - Kenneth A Oye and James H Maxwell
Heterogeneities at Two Levels - Ronald B Mitchell
State, Non-state Actors and Intentional Oil Pollution