When examining institutions, we often wish we could create a counterfactual world--a world where everything but the institution itself is the same. Using agent-based models--computational models where we assign computer agents simple rules in a world we create and watch them interact--allows us to create and re-create the world as we see fit. Examining how party system size affects the way in which networks influence voter turnout, we use an extension of Fowler's Turnout in A Small World agent-based model to show that third-party entry can have a negative effect on turnout. We then test an element of the model using empirical (observable) data
