STRATEGIC CANDIDACY AND SINGLE‐PEAKEDNESS*

In elections, the voting outcomes are affected by strategic entries of candidates. We study a class of voting rules immune to strategic candidacy. Dutta et al. (2001 ) show that such rules satisfying unanimity are dictatorial if all orderings of candidates are admissible for voters’ preferences. When voters’ preferences are single‐peaked over a political spectrum, there exist non‐dictatorial rules immune to strategic candidacy. An example is the rule selecting the m‐th peak from the left among the peaks of voters’ preferences, where m is any natural number no more than the number of voters. We show that immunity from strategic candidacy with basic axioms fully characterizes the family of the m‐th leftmost peak rules.     

STRATEGY‐PROOF ALLOCATION OF INDIVISIBLE GOODS AMONG COUPLES

We consider the problem of allocating indivisible goods among couples. Agents in a couple share the indivisible good assigned to them. The main result is that an allocation rule is strategy‐proof, neutral and non‐bossy if and only if it is serially dictatorial. An allocation rule is serially dictatorial if there is a priority order of couples and a function that identifies who chooses in each couple, such that for all preference profiles, a good assigned to couple i is the best element according to the preference of the identified agent in couple i among the remaining goods when the couples with higher priorities have made their choice.     

ENDOGENOUS TIME PREFERENCE,INTEREST‐RATE RULES,AND INDETERMINACY*

This paper extends the Benhabib et al. flexible‐price, money‐in‐the‐utility‐function model by considering endogenous time preference and re‐examines equilibrium indeterminacy in response to alternative interest‐rate rules. We show that either an active or a passive interest‐rate feedback rule can generate local indeterminacy even if consumption and real money balances are Edgeworth independent. This result is in sharp contrast to that in the related literature. We also find that in the presence of endogenous time preference, local indeterminacy may occur regardless of whether the monetary policy is based on the interest‐rate feedback rule or money growth‐rate targeting.     

Stable Assignment of Public Facilities under Congestion

We study the problem of locating multiple public facilities when each member of society has to be assigned to exactly one of these facilities. Individuals' preferences are assumed to be single‐peaked over the interval of possible locations and negatively affected by congestion. We characterize strategy‐proof, efficient, and stable allocation rules when agents have to be partitioned between two groups of users and discuss the normative content of the stability property. Finally we prove that when more than two groups have to be formed, even with common information on the distribution of the peaks, there is no strategy‐proof, efficient, and stable allocation rule.     

A Strategy‐Proofness Characterization of Plurality Rule

Assuming at least four individuals and at least four alternatives, a social choice function on the domain of profiles at which there is an alternative ranked first by more individuals than any other alternative is nondictatorial, strategy‐proof, and has full range if and only if it is plurality rule.     

Necessary and sufficient conditions for a resolution of the social choice paradox

We present a restriction on the domain of individual preferences that is both necessary and sufficient for the existence of a social choice rule that is continuous, anonymous, and respects unanimity. The restriction is that the space of preferences be contractible. Contractibility admits a straightforward intuitive explanation, and is a generalisation of conditions such as single peakedness, value restrictedness and limited agreement, which were earlier shown to be sufficient for majority voting to be an acceptable rule. The only restriction on the number of individuals, is that it be finite and at least 2.     

Strategy-proofness of the plurality rule over restricted domains

We give a complete characterization of preference domains over which the plurality rule is strategy-proof. In case strategy-proofness is required to hold under all tie-breaking rules, strategy-proof domains coincide with top-trivial ones where the range of the plurality rule admits at most two alternatives. This impossibility virtually prevails when strategy-proofness is weakened so as to hold under at least one tie-breaking rule: unless there are less than five voters, the top-triviality of a domain is equivalent to the (weak) non-manipulability of the plurality rule. We also characterize the cases with two, three or four voters. I am grateful to Attila Tasnadi for his thorough reading of the paper and pointing to an error in an earlier version. I thank Levent Kutlu, Clemens Puppe, Arunava Sen, an anonymous referee and an anonymous AE for their comments. This research is part of the project “Social Perception—A Social Choice Perspective” supported by Istanbul Bilgi University Research Fund. I also acknowledge the support of the Turkish Academy of Sciences Distinguished Young Scientist Award Program (TUBA-GEBIP).     

The structure of strategy-proof social choice — Part I: General characterization and possibility results on median spaces

We define a general notion of single-peaked preferences based on abstract betweenness relations. Special cases are the classical example of single-peaked preferences on a line, the separable preferences on the hypercube, the “multi-dimensionally single-peaked” preferences on the product of lines, but also the unrestricted preference domain. Generalizing and unifying the existing literature, we show that a social choice function is strategy-proof on a sufficiently rich domain of generalized single-peaked preferences if and only if it takes the form of voting by issues (“voting by committees”) satisfying a simple condition called the “Intersection Property.”Based on the Intersection Property, we show that the class of preference domains associated with “median spaces” gives rise to the strongest possibility results; in particular, we show that the existence of strategy-proof social choice rules that are non-dictatorial and neutral requires an underlying median space. A space is a median space if, for every triple of elements, there is a fourth element that is between each pair of the triple; numerous examples are given (some well-known, some novel), and the structure of median spaces and the associated preference domains is analysed.     

Group identification with (incomplete) preferences

We consider the problem of identifying members of a group based on individual opinions. Since agents do not have preferences in the model, properties of rules that concern preferences (e.g., strategy‐proofness and efficiency) have not been studied in the literature. We fill this gap by working with a class of incomplete preferences derived directly from opinions. Our main result characterizes a new family of group identification rules, called voting‐by‐equitable‐committees rules, using two well‐known properties: strategy‐proofness and equal treatment of equals. Our family contains as a special case the consent rules (Samet & Schmeidler. J. Econ. Theory, 110 (2003), pp. 213–233), which are symmetric and embody various degrees of liberalism and democracy; and it also includes dictatorial and oligarchic rules that value agents’ opinions differently. In the presence of strategy‐proofness, efficiency turns out to be equivalent to non‐degeneracy (i.e., any agent may potentially be included or excluded from the group). This implies that a rule satisfies strategy‐proofness, efficiency, and equal treatment of equals if, and only if, it is a non‐degenerate voting‐by‐equitable‐committees rule.     

A characterization of consistent collective choice rules

We characterize a class of collective choice rules such that collective preference relations are consistent. Consistency is a weakening of transitivity and a strengthening of acyclicity requiring that there be no cycles with at least one strict preference, which excludes the possibility of a “money pump.” The properties of collective choice rules used in our characterization are unrestricted domain, strong Pareto, anonymity and neutrality. If there are at most as many individuals as there are alternatives, the axioms provide an alternative characterization of the Pareto rule. If there are more individuals than alternatives, however, further rules become available.     

Strategy Proof Scoring Rule Lotteries for Multiple Winners

We develop a lottery procedure for selecting multiple winners that is strategy proof. The rule assigns points to each candidate based on any standard scoring rule method, and then uses one draw to select a single winning set of candidates in proportion to their collective score. In addition to being strategy proof, the lottery rule is also shown to have several other attractive normative properties. Violations of some other important normative properties are noted as well.     

Random dictatorship domains

A domain of preference orderings is a random dictatorship domain if every strategy-proof random social choice function satisfying unanimity defined on the domain is a random dictatorship. Gibbard (1977) showed that the universal domain is a random dictatorship domain. We ask whether an arbitrary dictatorial domain is a random dictatorship domain and show that the answer is negative by constructing dictatorial domains that admit anonymous, unanimous, strategy-proof random social choice functions which are not random dictatorships. Our result applies to the constrained voting model. Lastly, we show that substantial strengthenings of linked domains (a class of dictatorial domains introduced in Aswal et al., 2003) are needed to restore random dictatorship and such strengthenings are “almost necessary”.     

Super‐Majorites,One‐Dimensional Policies,and Social Surplus

In the setting of a one‐dimensional legislative bargaining game, we characterize qualified majority rules maximizing social surplus, that is, the sum of individual benefits. The simple majority rule maximizes social surplus when individual utilities are tent‐shaped. When the utilities are strictly concave, the surplus maximizing rule is a strict supermajority.     

Are property rights enough?Re‐evaluating a big‐bang claim1

We investigate the claim made by proponents of the big‐bang strategy that the establishment of property rights in an economy in transition creates its own demand for the enforcement of laws to protect those rights. Our model contains a government engaging in activities to accomplish objectives that depend on public support for the enforcement of the rule of law and agents who interpret the level of activities of the government as indications of the government's intent to enforce the rule of law. Agents, using the level of government activities as an input to their decisions, choose whether to support the government's objectives. We establish conditions under which the level of activities chosen by the government maximizes its benefits, and simultaneously induces the constituency to support enforcement of the rule of law. These conditions provide a basis for the argument for the implementation of the big‐bang policy. When these conditions do not hold, however, we show that the level of activities that maximizes the government's benefits may have only a minor impact on support for the enforcement of the rule of law. Two characteristics play an important role in these conditions: the initial level of crime and the types of activities the government chooses to undertake. We present examples showing that the initial level of crime has the more dramatic effect on subsequent support for the rule of law.     

REVEALED PREFERENCE AND ACTIVITY RULES IN DYNAMIC AUCTIONS

Activity rules—constraints that limit bidding in future rounds based on past bids—are intended to limit strategic bidding delays in high-stakes auctions. This article provides a general treatment of activity rules. Traditional point-based rules are effective for homogeneous goods and reasonably suited for substitute goods. However, they are simultaneously too strong and too weak for general environments; they allow parking, while sometimes preventing straightforward bidding. We prove that the activity rule operationalizing the generalized axiom of revealed preference (GARP) is essentially the unique rule that enforces the Law of Demand while enabling straightforward bidding and never producing “dead ends.”     

Profiteering from the Dot‐Com Bubble,Subprime Crisis and Asian Financial Crisis

The paper explores the characteristics associated with the formation of bubbles that occurred in the Hong Kong stock market in 1997 and 2007, as well as the 2000 dot‐com bubble of Nasdaq. It examines the profitability of technical analysis (TA) strategies generating buy and sell signals, with and without our proposed trading rules. The empirical results show that, by applying long and short strategies during the bubble formation and a short strategy after the bubble burst, it not only produces returns that are significantly greater than buy‐and‐hold strategies, but also produces greater wealth compared with TA strategies without trading rules. We conclude that these bubble detection signals help investors generate greater wealth from applying appropriate long and short moving average (MA) strategies.     

PLATFORM PRICING IN MIXED TWO‐SIDED MARKETS

When a consumer can appear on both sides of a two‐sided market, such as a user who both buys and sells on eBay, the platform may want to bundle the services it provides to two sides. I develop a general model for such “mixed” two‐sided markets and show that a monopolist platform's incentive to bundle and its optimal pricing strategy are determined by simple formulas using familiar price elasticities of demand, which embody the bundling effect, and price‐cost margins adjusted for network externalities, which incorporate “two‐sidedness.” The optimal pricing rule in such markets generalizes the familiar Lerner formula.     

Optimal sequential contract with a risk‐averse supplier

We study optimal contracts in environments where a risk‐averse supplier discovers cost information privately and gradually over time: the supplier is privately informed about its cost uncertainty at the time of contracting and discovers the realization of cost condition privately after contracting and before production. We show that both the buyer and the supplier prefer more cost uncertainty when the supplier is not very risk‐averse but less cost uncertainty when the supplier is sufficiently risk‐averse. However, the buyer always prefers to contract before the cost uncertainty resolves regardless of the supplier's degree of risk aversion. The nature of the optimal contract also depends on the supplier's risk preference. A separating contract is optimal when the supplier is not very risk‐averse; however, a pooling contract, which offers the same contract terms regardless of the cost uncertainty, can be optimal when the supplier becomes sufficiently risk‐averse. Moreover, the optimal production schedule is often characterized by “inflexible rules.”     

Extraneous Alternatives And Strategy-Proofness

It is well known that the Gibbard–Satterthwaite theorem cannot be circumvented by adding extraneous alternatives that are included in the individual preference information but are never selected. We generalize this by proving that, for any domain on which every strategy-proof rule is dictatorial, the addition of extraneous alternatives will not permit the construction of a non-dictatorial and strategy-proof rule if the new domain is a product set. We show how this result, and our other theorem, can be applied to seven families of social choice situations, including those in which more than one alternative is selected.     

Non-monotoniticies and the all-pay auction tie-breaking rule

Discontinuous games, such as auctions, may require special tie-breaking rules to guarantee equilibrium existence. The best results available ensure equilibrium existence only in mixed strategy with endogenously defined tie-breaking rules and communication of private information. We show that an all-pay auction tie-breaking rule is sufficient for the existence of pure strategy equilibrium in a class of auctions. The rule is explicitly defined and does not require communication of private information. We also characterize when special tie-breaking rules are really needed.