Evidence Design principle† Support 1 0 N P‡ Ratio§ Effect size| 1A. Clearly defined boundaries: Individuals or households who have rights to withdraw resource units from the common-pool resource (CPR) must be clearly defined. Success 31 2 63 < 0.0001 5.3 0.692 Failure 8 22         1B. Clearly defined boundaries: The boundaries of the CPR must be well defined. Success 22 4 42 0.049 2.2 0.313 Failure 9 7         2A. Congruence between appropriation and provision rules and local conditions: Appropriation rules restricting time, place, technology, and/or quantity of resource units are related to local conditions. Success 20 0 30 0.001 5.0 0.737 Failure 5 5         2B. Congruence between appropriation and provision rules and local conditions: The benefits obtained by users from a CPR, as determined by appropriation rules, are proportional to the amount of inputs required in the form of labor, material, or money, as determined by provision rules. Success 11 1 22 0.002 10.0 0.632 Failure 1 9         3. Collective-choice arrangements: Most individuals affected by the operational rules can participate in modifying the operational rules. Success 20 6 49 0.001 2.8 0.466 Failure 7 16         4A. Monitoring: Monitors are present and actively audit CPR conditions and appropriator behavior. Success 32 3 63 < 0.0001 3.8 0.587 Failure 10 18         4B. Monitoring: Monitors are accountable to or are the appropriators. Success 27 2 38 < 0.0001 11.7 0.792 Failure 1 8         5. Graduated sanctions: Appropriators who violate operational rules are likely to be assessed graduated sanctions (depending on the seriousness and context of the offense) by other appropriators, officials accountable to these appropriators, or both. Success 13 4 36 0.019 2.3 0.398 Failure 7 12         6. Conflict-resolution mechanisms: Appropriators and their officials have rapid access to low-cost local arenas to resolve conflicts among appropriators or between appropriators and officials. Success 26 2 42 0.01 3.2 0.429 Failure 8 6         7. Minimal recognition of rights to organize: The rights of appropriators to devise their own institutions are not challenged by external governmental authorities. Success 28 3 51 0.032 2.2 0.311 Failure 13 7         8. Nested enterprises: Appropriation, provision, monitoring, enforcement, conflict resolution, and governance activities are organized in multiple layers of nested enterprises. Success 27 4 51 0.065 2.0 0.262 Failure 13 7

†The language used to describe each principle follows that of Ostrom (1990:90).
‡Significance of Fisher’s exact test between the evidence and success variables.
§The number of supportive cases (main diagonal) to unsupportive cases (off-diagonal).
|The effect size was determined using the phi statistic, which is similar in interpretation to a beta coefficient in a standard regression.