I write this for use in modeling how and when groups will advocate policy change. I doubt that this description is exhaustive, but it should serve as a solid foundation for modeling group behavior with regards to collective action. My source for most of these descriptions is Analyzing Politics by Kenneth Shepsle.

Mancur Olson’s analysis in The Logic of Collective Action describes three principles of group efforts:

• The individuals have a common interest

• There is limited individual efficacy; each individual is almost powerless.

• Individuals cannot be excluded from the benefits of successful group action regardless of whether or not the individuals participate in the group’s action.

Issues that can be solved by small groups under these conditions are much more likely to be solved than issues that can only be solved by large groups. After all, the third point invites a collective action problem; if all can benefit without investing effort, few will be willing to invest effort. So, large groups will be more reluctant to form than small groups because everyone will be reluctant to join and invest effort into collective action. So, small groups end up being more powerful than large groups.

But if Olson’s theory holds, how can any collective action occur if the collective action problem is real? Mancur Olson, Richard Wagner, and Kenneth Shepsle advocate three ways that groups can form despite these three conditions.

Olson advocates By-Product Theory, in which the benefits of collective action are selectively awarded only to those helped fight for those benefits. In this case, everyone who wanted the benefits would support the group, and the collective action problem would be circumvented. (Technically, this is more of a way to get around the third point than to operate within that limitation, but oh well.)

Richard Wagner advocates political entrepreneurs as another way to circumvent Olson’s problem. Wagner suggests that enterprising individuals will fight for public benefits in exchange for private benefits. And with a leader spearheading the collective action, others will be more willing to join the group because the leader can guarantee turnout. For example, take democratically elected representatives, who fight for public benefits in exchange for election to paid government positions.

Kenneth Shepsle suggests that political institutions can pursue the same goal as political entrepreneurs: fighting for public policy decisions while gaining private benefits. For example, take political lobbies such as Greenpeace.

So, any simulation of collective action should take at least these three methods of defeating the collective action problem into account.

EDIT: making my grammar gooder.