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Social-Ecological Systems Meta-Analysis Database: Theory

Group size and collective action

Variable relationship:

Group size (Group Size) affects cooperative management of environmental commons in several ways. As discussed by Olson (1965), group size increases the transaction costs (Transaction Costs) of decision making and monitoring increase, and decreases the chances of successful collaborative governance (Collective Action). Within CPR theory (e.g. Poteete et al. 2004), this relationship has mostly been discussed within the context of community-based natural resource management, and the theory explains variation in the abilities of different groups to act collectively in order to manage their own resource. As group size decreases, it is plausible to think that interactions between users increase, which consequently increases the importance of reputation in the group and facilitates monitoring, and that it is easier to monitor other users.

Also, heterogeneity (see Interest Heterogeneity and Cultural Heterogeneity theories) is likely to increase with group size, and with it also the chances of disagreements over the management of the commons. However, while there is consensus on the fact that group size and heterogeneity influence the likelihood of collective action -in particular the level of trust and of convergence of interests- there is no such consensus about the particular effect which these variables have and how does context (i.e. different combinations with other variables, including institutions themselves) mediate the effect of group size (Agrawal 2001; Poteete and Ostrom 2004). Theoretically, while larger group size leads to a decreased individual contribution, it also leads to an increased collective provision, making larger investments more feasible (see Poteete and Ostrom 2004). Finally, as shown by social movements scholars, larger groups also have more political power, potentially contributing to enhanced local autonomy to devise locally-appropriate institutions.

Within the literature on policy instrument choice and environmental governance, it is mentioned that the size of the group that is the target of a policy is similarly important. For example, with taxes or subsidies and PES schemes, the greater the number of individuals taxed or subsidized, the higher the transaction costs involved, and the more difficult it can be to successfully implement the policy.

Additionally, heterogeneity is likely to increase with group size, and with it also comes the possibility for disagreements over the management of the commons. 

Scientific Field
Component Type(s)


VariableRoleRole ExplanationValue
Actor group sizeUnderlying independent variableThe smaller the group the easier to design management rules and to monitor compliance Small
Transaction costsProximate independent variableSmaller groups face lower transaction costs (e.g., for monitoring, decision making...)Low
Collective actionIntermediate outcomeLow transaction costs of decision making and monitoring facilitate cooperation vis a vis resource management. This is more applicable to local self-governance cases than cases where the group in question is the target of a policy.High
Commons condition trendFinal outcomeHigh levels of cooperation help to sustain the commons that is being managed.Remained the same or improved.

Related Theories

TheoryRelationshipCharacterizing Variables
Community-based natural resource management (CBNRM)nested
Transaction costs and collective actioncontains

Related Studies


Agrawal, Arun. 2001. "Common Property Institutions and Sustainable Governance of Resources."  World Development 29 (10):1649-1672.


Poteete, Amy R., and Elinor Ostrom. 2004. "Heterogeneity, Group Size and Collective Action: The Role of Institutions in Forest Management."  Development and Change 35 (3):435-461. doi: 10.1111/j.1467-7660.2004.00360.x.


Olson, Mancur. 1965. The Logic of Collective Action. Cambridge: Massachussetts: Harvard University Press.