Agent-based Simulation of District-based Elections with Heterogeneous Populations

Adway Mitra

Abstract: In district-based elections, voters cast votes in their respective districts. In each district, the party with maximum votes wins the corresponding "seat" in the governing body. The election result is based on the number of seats won by different parties. In this system, locations of voters across the districts may severely affect the election result even if the total number of votes obtained by different parties remains unchanged. A less popular party may win more seats if their supporters are suitably distributed spatially. This happens due to various regional and social influences on individual voters which modulate their voting choice, especially in heterogeneous societies. In this paper, we explore agent-based models for district-based elections, where we consider each voter as an agent, and try to represent their social and geographical attributes and political inclinations using probability distributions. We propose several models which aim to represent one or more of these aspects. These models can be used to simulate election results by Monte Carlo sampling. The models allow us to explore the possible outcomes of an election, and can be calibrated to actual election results for suitable values of parameters obtained by Approximate Bayesian Computation. Our model can reproduce results of elections in India and USA, and also simulate counterfactual scenarios.