CONCEPT
Common-Pool Resource
The institutional-economic category for resources exhibiting both subtractability (one user's consumption reduces availability to others) and difficulty of exclusion (excluding potential users is costly or impractical) — the definitional test that determines whether a resource system faces the governance dilemma Ostrom analyzed.
A common-pool resource (CPR) is not defined by ownership but by two structural characteristics. Subtractability means that resource units consumed by one user are not available to others — fish caught by one boat, water diverted by one irrigator, attention given to one piece of content. Difficulty of exclusion means that preventing use by non-members is expensive or impractical — ocean fisheries are too vast to patrol, irrigation systems serve many users who cannot easily be disconnected, knowledge environments cannot be fully gated. Together these characteristics create the governance dilemma: because exclusion is difficult, the resource is vulnerable to overuse; because use is subtractive, overuse degrades the resource for everyone.
In The You On AI Field Guide
CPRs sit between private goods (excludable, subtractive) and public goods (non-excludable, non-subtractive) in the institutional-economics taxonomy. Their governance has always been the most analytically contested, because neither market mechanisms nor standard public-goods provision adequately addresses the