Nonlinear effects of group size on collective action and resource outcomes - PubMed (original) (raw)

Nonlinear effects of group size on collective action and resource outcomes

Wu Yang et al. Proc Natl Acad Sci U S A. 2013.

Abstract

For decades, scholars have been trying to determine whether small or large groups are more likely to cooperate for collective action and successfully manage common-pool resources. Using data gathered from the Wolong Nature Reserve since 1995, we examined the effects of group size (i.e., number of households monitoring a single forest parcel) on both collective action (forest monitoring) and resource outcomes (changes in forest cover) while controlling for potential confounding factors. Our results demonstrate that group size has nonlinear effects on both collective action and resource outcomes, with intermediate group size contributing the most monitoring effort and leading to the biggest forest cover gain. We also show how opposing effects of group size directly and indirectly affect collective action and resource outcomes, leading to the overall nonlinear relationship. Our findings suggest why previous studies have observed differing and even contradictory group-size effects, and thus help guide further research and governance of the commons. The findings also suggest that it should be possible to improve collective action and resource outcomes by altering factors that lead to the nonlinear group-size effect, including punishing free riding, enhancing overall and within-group enforcement, improving social capital across groups and among group members, and allowing self-selection during the group formation process so members with good social relationships can form groups autonomously.

Keywords: biodiversity conservation; casual inference; commons governance; ecosystem services; sustainability.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.

Fig. 1.

Hypothetical effects of free riding, within-group enforcement, and group size on collective action and resource outcomes. Both free riding and within-group enforcement are hypothesized to be positively related to group size. However, free riding is hypothesized to be negatively related to within-group enforcement. The combined effects of free riding and within-group enforcement on collective action and resource outcomes are not expected to be additive because of interactions between within-group enforcement and free riding. The net effect of group size is determined by the dynamics (e.g., strength and variation with group size) of free riding and within-group enforcement, which may form a nonlinear pattern.

Fig. 2.

Fig. 2.

Map of the location, main road, forest cover in 2007, and household monitoring parcels of Wolong Nature Reserve in Sichuan Province, China.

Fig. 3.

Fig. 3.

The nonlinear group-size effects on collective action and forest outcomes. This figure shows the predicted monitoring effort (A) and forest-cover change (B) from 2001 to 2007 under different group sizes (i.e., number of households monitoring a single forest parcel). The graphs show the net effects of group size on per household monitoring effort and on change in forest cover, while controlling the other variables in Tables 1 and 2. The blue line is the predicted fit based on group size, and the orange dots are the actual observations. One dot may represent several overlapping observations. Except for linear and quadratic terms of group size, all other independent variables were controlled as their mean values (

SI Appendix, Tables S1 and S3

). In B our conclusion still holds as the nonlinear effect is still significant even when excluding the parcels with group size of one, or the two parcels with group sizes of 15 and 16 (see details in

SI Appendix, Section 2.5.2

). However, for A and B, the observations do not visually fit the predicted lines in the same way as the observations in ordinary least-squares regressions (54) because these models are not ordinary least-squares regressions (see details in

SI Appendix, Section 2.5

).

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References

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