Fig. 2: The evolution of collective property rights.

a, The effect of heterogeneity in patch size (exogenously controlled) on roving banditry (boundaries disabled). b, The effect of MAH policies (exogenously controlled) on roving banditry (access rights disabled). c, Investments in access rights (seizures disabled). Lines show the average investment in access rights for a single group in a single simulation. d, Investment in access rights (seizures enabled). e, Results from the difference equations with parameters set to sustain the resource above a threshold: enforcement of access rights in blue, resource stock in green and bandits in red. f, Replicates e while improving harvesting technology, causing the resource to fall below a critical threshold, impairing the stability of access rights. g, The relationship between roving banditry (exogenously controlled) and investment in monitoring use rights (access rights disabled). h, The relationship between access rights (exogenously controlled) and investment in monitoring use rights. i–l, The effect of out-group learning (exogenously controlled) on investment in monitoring use rights (i), MAH policies (j), resource stock levels (k) and payoffs (l). m, The covariance between MAH policy and payoffs. Black points marked as ‘not enforced’ have a low investment in self-regulation (R ≤ 0.5) and orange points marked as ‘enforced’ are those that have stabilized support (R > 0.5). n, Tipping point in payoffs as a function of stock level (MSY). o, Groups’ search processes for a sustainable MAH (rate of roving banditry is low (exogenously controlled)). Green lines show intact resources and turn black once the resource has collapsed (‘stock’ ≤ 0.05 maximum capacity). p, Replicates o but with roving bandits allowed (exogenously controlled). We use 100 groups on a 10 × 10 lattice for all simulations, with 30 individuals per group. In g–l, each point is the average value in the last 1,000 time steps of the y axis variable from a single simulation after a 4,000-round burn-in. Lines show the average across all simulations. Enf., enforced. For the parameter configuration used, see Methods and Supplementary Information; for full parameter sweep, see Supplementary Information.