The Number of Parties and Decision-Making in Legislatures

Marina Bannikova,Artyom Jelnov,Pavel Jelnov

doi:10.3390/g12040076

Abstract

This paper proposes a model of a legislature, formed by several parties, which has to vote for or against a certain bill in the presence of a lobbyist interested in a certain vote outcome. We show that the ease with which the lobbyist can manipulate a legislature decision increases with the number of elected parties, and, consequently, decreases with an electoral threshold. On the other hand, a lower electoral threshold increases the representativeness of a legislature. We combine these two effects in a notion of fairness. We show the existence of an electoral threshold that optimizes the fairness of a political system, which is close to 1–5%. Namely, the optimal threshold (in our sense) is close to thresholds that exist in most parliamentary democracies.

Highlights

We study the effect of the electoral threshold on the ease of a lobbyist influencing a voting outcome, through its impact on the number of parties in the legislature
We assume that the lobbyist tries to manipulate the legislature decision by offering payment to parties for a change
We focus on the electoral threshold, but other parameters of a legislature are important

Summary

Introduction

Some decisions only affect a decision-maker and his utility. others may affect more people and, their utilities too. Every citizen of a democratic country supports a certain candidate or a party in order to delegate to them his decision power The voter puts his trust in the representative, based on electoral campaign statements. We study the effect of the electoral threshold on the ease of a lobbyist influencing a voting outcome, through its impact on the number of parties in the legislature. We assume that the lobbyist tries to manipulate the legislature decision by offering payment to parties for a change. To the best of our knowledge, this is the first justification by a mathematical model of electoral thresholds of 1–5% that exist in most parliamentary democracies It is not clear how vulnerability of a political system for manipulation can be tested empirically. Ref. [27] studies loss aversion and attitude to political decisions

Number of Parties

Analytical Result

Numerical Result

Given Electoral Threshold

Final Remarks