理论论文

We study priority-based matching markets with public and private endowments. We show that efficiency-adjusted deferred acceptance (EADA) is justified-envy minimal in the class of efficient mechanisms, while Top trading cycles (TTC) and other popular mechanisms are not. Our findings highlight EADA as an interesting alternative to TTC in the context of transplantation-organ markets. Restricting attention to strategyproof mechanisms, we show that TTC is justified-envy minimal, strengthening the result of Abdulkadiroglu et al. (2020).

In a game in extensive form, we say that a sequence of trembles destabilizes an outcome if there is no corresponding sequence of payoff perturbations and Nash outcomes converging to the outcome. We use equilibrium destabilization to characterize sequential equilibria and sequentially stable outcomes, and to reinterpret standard selection criteria in signaling games as a means of ruling out implausible equilibria by identifying destabilizing tremble sequences. We show that the existence of a maximally destabilizing sequence of trembles (destabilizing all outcomes but one) significantly simplifies studying strategically stable behavior in complex games such as finitely repeated games.

By showing that a one-shot deviation property holds for almost all large games with i.i.d. randomly drawn payoffs in which a convention (in the sense of Young, 1993a) exists, long-run outcomes under behavioral rules are characterized by social choice rules.

In the context of one-to-one matching markets, we study myopic-farsighted stable sets, which are internally and externally stable when myopic agents consider immediate payoffs from their deviations, while farsighted agents anticipate counter-deviations and consider final payoffs. We constructively prove the existence of a (rational expectations) myopic-farsighted stable set, in which farsighted agents receive a single payoff while myopic agents may receive multiple payoffs. Our existence result extends to settings with enforcing coalitions of arbitrary size, yielding coalitional myopic-farsighted stable sets, and to settings where not all members of an enforcing coalition must strictly gain, yielding myopic-farsighted weakly stable sets. When all farsighted agents have unit demand, our results also extend to many-to-one matching markets. As a key corollary, we provide a foundation for the efficiency-adjusted deferred acceptance algorithm by showing that its outcome constitutes a singleton myopic-farsighted stable set when one side is farsighted and the other is myopic.

ABSTRACT Borrowers' use of cashless payments improves their access to capital from FinTech lenders and predicts a lower probability of default. These relationships are stronger for cashless technologies providing more precise information, and for outflows. Cashless payment usage complements other signals of borrower quality. We rationalize these empirical findings using a framework in which borrowers signal their lower likelihood of diverting cash flows through payment technology choice, and screening accuracy is further strengthened by informational complementarities. The informational synergy we uncover provides a rationale for the joint rise of cashless payments and FinTech lending, as well as for open banking.

In school choice problems, the pursuit of student welfare (efficiency) is constrained by the requirement to respect schools’ priorities (fairness). Among fair matchings, even the welfare maximizing one, the Student-Optimal Stable Matching (SOSM), is inefficient. Moreover, any mechanism that yields welfare gains over the SOSM is manipulable by students. This paper investigates the fairness and incentive properties of efficient mechanisms. We compare matchings using the notion that one matching is less unfair than another if it generates a smaller set of students whose priorities are violated, and we define minimal unfairness accordingly. We show that the Efficiency-Adjusted Deferred Acceptance (EADA) mechanism is minimally unfair within the class of Pareto efficient mechanisms satisfying a simple incentive requirement, top-manipulation-proofness. Moreover, the EADA satisfies a stronger property, upper-manipulation-proofness. Upper-manipulation-proofness is a broad incentive property one can maintain while improving upon the SOSM. Together, these results highlight a sharp frontier in school choice: when the objective is efficiency and improving student welfare over the SOSM, the EADA emerges as a compelling mechanism in both fairness and incentive terms.

We prove a Folk theorem when players with bounded rationality learn as they play a repeated potential game. We use a dynamic generalization of smooth fictitious play with bounded $m$-memory strategies to model learning with bounded rationality that is consistent with learning by algorithms. In a repeated potential game with perfect monitoring, we use this learning model to show that for any feasible and individually rational payoff profile, if players have sufficient memory, are sufficiently patient, and best respond with sufficiently few mistakes, then the players have a non-zero probability of learning an $m$-memory strategy profile that achieves an average payoff close to the specified payoff profile for an appropriate continuation game. Moreover, the strategy profile learned is an $m$-memory $\epsilon$-subgame perfect equilibrium of the repeated game. This finding demonstrates that competition authorities are correct in their concern about algorithmic collusion.

This paper analyzes the extent to which well-known results on the relationship between the bargaining set, the core, and the kernel in one-to-one assignment games generalize to many-to-one assignment markets, and by extension, many-to-many markets. Using a minimal counterexample, we show that the bargaining set does not necessarily coincide with the core and that the kernel may not be contained within the core. We would like to highlight that the failure of the coincidence between the core and the bargaining set, as observed in the many-to-one assignment game, is quite notable. This is especially true when compared to various other highly structured games, many of which emerge from combinatorial optimization problems, such as the one underlying many-to-one assignment games.

We analyze risk-taking behaviors of financial institutions linked through cross-shareholding relationships. We endogenize risk exposure accounting for default risk by modeling Value-at-Risk-based risk-management – that is targeted default probabilities – in the presence of extreme risk on asset return. We relate risk-taking behaviors to a centrality measure that captures the propagation of losses within the network, and show that network integration increases risk-taking levels and expected return. However, we show that network integration also results in larger expected shortfall, indicating greater exposure to losses for creditors. We explore the impact of the cross-shareholding network on the implementation of regulation, particularly through capital requirements, and identify key institutions, those with the highest influence on aggregate investments in risky assets.

Parties in primary elections often choose between candidates who appeal to their base and those who appeal to the broader electorate. I present a model of primaries where incumbents can exploit this trade-off the opposition faces between ideological congruence and electability. In the model, incumbents reduce their appeal to the median voter by moving away from the center. In doing so, they provoke the opposition into nominating extremists, improving their reelection prospects. This mechanism generates elite polarization as politicians leapfrog voters — not despite electoral concerns, but because of them. The analysis fits the observation that incumbents sometimes move away from the center near the end of their term. Provoking the opposition relies on two conditions: divergence of primary and general electorates and a limited set of potential nominees. I argue that partisan sorting and changes in nomination procedures over the last decades made this strategy viable.

Economists often rely on people’ s choices to infer their preferences. However, inferring preferences from choices becomes problematic when people face unobserved constraints. In this paper, I study how to (cautiously) infer preferences from choices when the choices of the members of a social group are subject to a constraint that we only imperfectly know. When this happens, heterogeneity in the group’ s choices, along with more information about the constraint, helps recover the preferences of group members, whereas homogeneity in choices hinders it. I further argue that standard approaches to choice-based welfare analysis can lead to misleading inferences about welfare when there are unobserved social constraints.

This paper analyzes the welfare properties of the mechanism Taiwan uses to match students to high schools. I study the Taiwan mechanism under a theoretical model where students share the same ordinal rankings, and a single lottery determines schools’ preferences. In this setting, all Taiwan mechanisms ex ante weakly Pareto dominate deferred acceptance for strategizing students. Additionally, in my model, there always exists a Taiwan mechanism that provides greater welfare than deferred acceptance to students who do not strategize. Using Cambridge Public School data, I demonstrate that the Taiwan mechanism outperforms deferred acceptance for a range of deduction rules.

We consider a market with indivisible objects, called houses, and monetary transfers. Each house is initially occupied by one agent and each agent demands exactly one house. The problem is to identify the complete set of direct allocation mechanisms that can be used to reallocate the houses among the agents. On the one hand, for price eq1uilibrium mechanisms, we show that the only non-manipulable mechanism is one with a minimum equilibrium price vector. The result is not true on the classic or the quasi-linear domains, but on reduced domains of preference profiles containing “almost all” profiles in the classic or the quasi-linear domain, respectively. On the other hand, while minimum price equilibrium mechanisms are not necessarily efficient (as prices are not zero), we show that no non-manipulable mechanism Pareto dominates a minimum price equilibrium mechanism, making them constrained efficient in the class of non-manipulable mechanisms.

We study the effects of local partisanship in a model of electoral competition. Voters care about policy, but they also care about the identity of the party in power, with most states biassed toward one party or the other (i.e., ‘red’ or ‘blue’). We show that electoral competition leads to maximization of welfare with an extra weight on citizens of the ‘swing state:’ the one that is not biassed toward either party. We show empirically that the US tariff structure is biassed toward swing-state industries, such that a voter living in a non-swing state is treated as being worth 82% as much as a voter in a swing state. This represents a policy bias orders of magnitude greater than the bias found in studies of protection for sale.

This paper examines how offshoring shapes emissions leakage and global emissions in response to unilateral environmental policy. We use a general equilibrium offshoring model with heterogeneous firms, based on standard modeling assumptions, where firms allocate labor between production tasks and emissions abatement. We find that global emissions respond non-monotonically to a unilateral emissions tax increase: for small cross-country tax differentials, emissions fall; but as the difference widens, leakage exceeds 100%, raising global emissions due to a global technique effect. The cleanest domestic firms start offshoring and incumbent offshoring firms become dirtier under declining effective foreign taxes. We isolate the offshoring margin – one underexplored channel of leakage – and contrast our findings with comparable models of trade in final goods: the mode of globalization matters. Complementing the unilateral reform with a border carbon adjustment (BCA) prevents emissions leakage but may raise inequality between countries.

We introduce the notion of preconvexity, which extends the familiar concept of convexity found in cooperative games with transferable utility. In a convex game, the larger the group joined by an agent, the larger the marginal value brought to the group by that agent. By contrast, in strictly preconvex games, an agent’s marginal contribution is initially decreasing (when joining small groups), and it eventually becomes increasing at (and above) some critical group size. As a consequence, the core of a preconvex game may be empty. Defining the property of semicohesiveness (related to marginal contributions at this critical group size), we prove that it is sufficient to guarantee a nonempty core. We also propose a new solution for the set of preconvex games; and we characterize this solution by combining three axioms which are natural in our framework. A stronger cohesiveness property (guaranteeing that our solution falls in the core) is also studied. Some additional results are provided for the special case of anticonvex games, for which marginal contributions are always non-increasing.

In this paper, we explore the issue of manipulability in the setting of financial systems by considering two weak forms of immunity: merging-proofness and splitting-proofness. Not surprisingly, splitting-proofness conflicts with basic requirements such as the priority of debt over equity and the limited liability of equity. Remarkably, we provide a comprehensive characterization of the class of bankruptcy rules that gives rise to financial rules that satisfy merging-proofness.

Faced with political opposition to efficient carbon pricing, climate policy resorts to alternative instruments, which come with welfare and fiscal costs of acceptability. To assess these costs, this study examines second-best policies combining a constant carbon tax with subsidies to carbon-free electricity generation and storage. Using a stylized dynamic model of the energy transition featuring fossil and clean energy sources and a carbon budget, we show that the lower the carbon tax, the greater the carbon pricing gap, and the larger the subsidies required to meet the carbon budget. Overaccumulation of clean capital may be needed to crowd out fossil fuels. Calibration to the European energy market reveals costs of acceptability up to 2.6% of welfare and a budget shortfall equivalent to 56% of the present value of electricity consumption. This suggests that relying on green subsidies for the energy transition may be unwise.

Most comparisons of preferences are instances of single-crossing dominance. We examine the lattice structure of single-crossing dominance, proving characterisation, existence and uniqueness results for minimum upper bounds of arbitrary sets of preferences. We apply these theorems to derive new comparative statics theorems for collective choice and under analyst uncertainty, and to characterise a general 'maxmin' class of uncertainty-averse preferences over Savage acts.

ABSTRACT We show that incorporating defined benefit pension funds in an incomplete markets asset pricing model improves its ability to match the historical equity premium and riskless rate and has important risk‐sharing implications. We document the importance of the pension fund's size and asset demands, and a new risk channel arising from fluctuations in the fund's returns. We use our calibrated model to study the implications of a shift to an economy with defined contribution plans. The new steady state is characterized by a higher riskless rate and a lower equity premium. Consumption volatility increases for retirees but decreases for workers.