How many candidates are needed to make elections hard to manipulate?

In multiagent settings where the agents have different preferences, preference aggregation is a central issue. Voting is a general method for preference aggregation, but seminal results have shown that all general voting protocols are manipulable. One could try to avoid manipulation by using voting protocols where determining a beneficial manipulation is hard computationally. The complexity of manipulating realistic elections where the number of candidates is a small constant was recently studied (Conitzer 2002), but the emphasis was on the question of whether or not a protocol becomes hard to manipulate for some constant number of candidates. That work, in many cases, left open the question: How many candidates are needed to make elections hard to manipulate? This is a crucial question when comparing the relative manipulability of different voting protocols. In this paper we answer that question for the voting protocols of the earlier study: plurality, Borda, STV, Copeland, maximin, regular cup, and randomized cup. We also answer that question for two voting protocols for which no results on the complexity of manipulation have been derived before: veto and plurality with runoff. It turns out that the voting protocols under study become hard to manipulate at 3 candidates, 4 candidates, 7 candidates, or never

Agenda Control in Coalition Formation

Theoretical models of government formation in political science usually assume that the head of state is non-strategic. In this paper, we analyze the power of an agenda setter who chooses the order in which players are recognized to form coalitions in simple games. We characterize those sets of players which can be imposed in the equilibrium coalition and show that the only decisive structures where the agenda setter can impose the presence of any minimal winning coalition are apex games, where a large player forms a winning coalition with any of the small players.Agenda Control; Cabinet Formation; Simple Games

A Smooth Transition from Powerlessness to Absolute Power

We study the phase transition of the coalitional manipulation problem for generalized scoring rules. Previously it has been shown that, under some conditions on the distribution of votes, if the number of manipulators is $o(\sqrt{n})$, where $n$ is the number of voters, then the probability that a random profile is manipulable by the coalition goes to zero as the number of voters goes to infinity, whereas if the number of manipulators is $\omega(\sqrt{n})$, then the probability that a random profile is manipulable goes to one. Here we consider the critical window, where a coalition has size $c\sqrt{n}$, and we show that as $c$ goes from zero to infinity, the limiting probability that a random profile is manipulable goes from zero to one in a smooth fashion, i.e., there is a smooth phase transition between the two regimes. This result analytically validates recent empirical results, and suggests that deciding the coalitional manipulation problem may be of limited computational hardness in practice.Comment: 22 pages; v2 contains minor changes and corrections; v3 contains minor changes after comments of reviewer

An Analysis of Political and Institutional Power Dispersion: The Case of Turkey

This study examines the effects of fragmented governments and fiscal authorities on budget deficits in Turkey along with political business cycle effects. For econometric analysis we will use annual data from the period of 1960-2009. This paper sheds light on various dispersion indices and their use in the field of political power and fiscal performance. The results show that the power dispersion indices of governments and fiscal institutions significantly explain the increases in the ratio of budget deficit to GNP. The paper draws attention to the unification and better coordination of fiscal authorities in Turkey. The analysis has important policy implications for Turkey and other developing countries from the viewpoint of fragmented political and administrative dispersion of power and poor budget performances.Political Business Cycles, Fragmentation and Power Dispersion, Public Budget, Turkey, Statistical Indices

An Analysis of Political and Institutional Power Dispersion: The Case of Turkey

This study examines the effects of fragmented governments and fiscal authorities on budget deficits in Turkey along with political business cycle effects. For econometric analysis we will use annual data from the period of 1960-2009. This paper sheds light on various dispersion indices and their use in the field of political power and fiscal performance. The results show that the power dispersion indices of governments and fiscal institutions significantly explain the increases in the ratio of budget deficit to GNP. The paper draws attention to the unification and better coordination of fiscal authorities in Turkey. The analysis has important policy implications for Turkey and other developing countries from the viewpoint of fragmented political and administrative dispersion of power and poor budget performances.Political Business Cycles, Fragmentation and Power Dispersion, Public Budget, Turkey, Statistical Indices

Collectively Incentive Compatible Tax Systems

This paper assumes that individuals possess private information both about their abilities and about their valuation of a public good. Individuals can undertake collective actions on order to manipulate the tax system and the decision on public good provision. Consequently, an implementable scheme of taxation has to be collectively incentive compatible. If preferences are additively separable, then an implementable tax systems has the following properties: (i) tax payments do not depend on public goods preferences and (ii) there is no scope for a collective manipulation of public goods preferences. For a quasilinear economy, the optimal tax system is explicitly characterized.Optimal Taxation, Public Good Provision, Revelation of Preferences, Information Aggregation

Proposal Rights and Political Power

In a canonical model of sequential collective bargaining over a divisible good we show that equilibrium expected payoffs are not restricted by players’ voting rights or their impatience. For all monotonic voting rules and discount factors, and for all divisions of the good among players, there exists a stationary proposal-making rule such that this division represents players’ expected payoffs in a Stationary Subgame Perfect Nash equilibrium in pure strategies. The result attests to the significance of proposal rights in determining political power in collective deliberations.Power, Proposal Rights, Voting Rights.