Predicting Voting Outcomes in Presence of Communities

Individuals in a social network may form their views as a result of the influence exerted by their connections. In elections, for example, while they might initially support one candidate, social influence may lead them to support another. Here, we investigate whether a recently proposed metric, influence gap, designed to measure the effect of social influence in voting on social networks, is able to predict the outcome of a vote on networks exhibiting community structure, i.e., made of highly interconnected components, and therefore more resembling of real-world interaction. To encode communities, we extend the classical model of caveman graphs to a richer graph family that displays levels of homophily, i.e., where connections and opinions are highly intertwined. We show that, across these graphs, there are important cases when the influence gap correlation is a weak predictor due to communities, and a simpler metric, counting the initial partisan majority, provides a more accurate prediction overall. Using regression models, we further demonstrate that the influence gap combined with the more successful metrics does increase their predictive power for some levels of homophily.