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Abstract
We test experimentally the Gale-Shapley Deferred Acceptance (DA) mechanism versus two versions of the Iterative Deferred Acceptance Mechanism (IDAM), in which students make applications one at a time. A significantly higher proportion of stable outcomes is reached under IDAM than under DA. The difference can be explained by a higher proportion of subjects following an equilibrium truthful strategy under iterative mechanisms than the dominant strategy of truthful reporting under DA. We associate the benefits of iterative mechanisms with the feedback on the outcome of the previous application they provide to students between steps.

We consider the hiring of public sector workers through legislated rules and exam-based rankings, as is done in many countries and institutions around the world. In them, workers take tests and are ranked based on scores in exams and other pre-determined criteria, and those who satisfy some eligibility criteria are made available for hiring in a "pool of workers." In each of an ex-ante unknown number of rounds, vacancies are announced and workers are then hired from that pool. We show that when the scores are the only criterion for selection, the procedure satisfies desired fairness and independence properties. We show, with the aid of details of procedures used in Brazil, France and Australia, that when compositional objectives are introduced, such as affirmative action policies, both the procedures used in the field and in the literature fail to satisfy those properties. We then present a new rule, which we show to be the unique rule that satisfies those properties. Finally, we show that if multiple institutions hire workers from a single pool, even minor consistency requirements are incompatible with compositional objectives.

O presente artigo analisa o impacto dos controles de capitais sobre a trajetória temporal de uma série de variáveis macroeconômicas para economias em desenvolvimento a partir de um modelo pós-keynesiano de economia aberta e sem governo. Inicialmente, apresentamos um modelo macroeconômico que introduz o controle de capitais como variável de escolha de política econômica. A partir da análise de estabilidade do modelo deduzimos um conjunto de valores economicamente plausíveis para os parâmetros. Com base nestes parâmetros analisamos o comportamento dinâmico do grau de utilização da capacidade produtiva, do endividamento externo, das exportações líquidas e da taxa de juros sob diferentes condições iniciais. Na seqüência, analisamos a sensibilidade da economia a choques externos como, por exemplo, variações da taxa de juros internacional e do fluxo internacional de comércio. Nesse contexto, constatamos que os controles de capitais podem contribuir para a redução da volatilidade da dívida externa a choques exógenos, mas amplificam os efeitos desses choques sobre o grau de utilização da capacidade produtiva. Desta forma, a desejabilidade da adoção de controles de capitais é condicional às preferências da sociedade no que se refere à volatilidade do grau de utilização da capacidade vis-à-vis à volatilidade do endividamento externo.

We consider the hiring of public sector workers through legislated rules and exam-based rankings, as is done in many countries and institutions around the world. In them, workers take tests and are ranked based on scores in exams and other pre-determined criteria, and those who satisfy some eligibility criteria are made available for hiring in a "pool of workers." In each of an ex-ante unknown number of rounds, vacancies are announced and workers are then hired from that pool. We show that when the scores are the only criterion for selection, the procedure satisfies desired fairness and independence properties. We show, with the aid of details of procedures used in Brazil, France and Australia, that when compositional objectives are introduced, such as affirmative action policies, both the procedures used in the field and in the literature fail to satisfy those properties. We then present a new rule, which we show to be the unique rule that satisfies those properties. Finally, we show that if multiple institutions hire workers from a single pool, even minor consistency requirements are incompatible with compositional objectives.

We run laboratory experiments where subjects are matched to colleges, and colleges are not strategic agents. We test the Gale-Shapley Deferred Acceptance (DA) mechanism versus the Iterative Deferred Acceptance Mechanism (IDAM), a matching mechanism based on a new family of procedures being used in the field, in which information about tentative allocations is provided while students make choices. We consider two variations of IDAM: one in which they are only informed about whether they are tentatively accepted or not (IDAM-NC) and one in which students are additionally informed at each step of the tentative cutoff values for acceptance at each school (IDAM). A significantly higher proportion of stable outcomes is reached both under IDAM and IDAM-NC than under DA. The difference can be explained by a higher proportion of subjects following an equilibrium strategy akin to truthful behavior under IDAM and IDAM-NC than truthful behavior itself under DA. Moreover, the provision of intermediate cutoff values in IDAM leads to higher rates of equilibrium behavior than in IDAM-NC and a higher robustness of stability between the rounds of experiments. Our findings provide substantial support for the rising practice of using iterative mechanisms in centralized college admissions in practice.

We show that Ergin & Sönmez's (2006) results which show that for schools it is a dominant strategy to truthfully rank the students under the Boston mechanism, and that the Nash equilibrium outcomes in undominated strategies of the induced game are stable, rely crucially on two assumptions. First, (a) that schools need to be restricted to find all students acceptable, and (b) that students cannot observe the priorities set by the schools before submitting their preferences. We show that relaxing either assumption eliminates the strategy dominance, and that Nash equilibrium outcomes in undominated strategies for the simultaneous induced game in case (a) and subgame perfect Nash equilibria in case (b) may contain unstable matchings. We also show that when able to manipulate capacities, schools may only have an incentive to do so if students submit their preferences after observing the reported capacities.

We introduce a new mechanism for matching students to schools or universities, denoted Iterative Deferred Acceptance Mechanism (IDAM), inspired by procedures currently being used to match millions of students to public universities in Brazil and China. Unlike most options available in the literature, IDAM is not a direct mechanism. Instead of requesting from each student a full preference over all colleges, the student is instead repeatedly asked to choose one college among those which would accept her given the current set of students choosing that college. Although the induced sequential game has no dominant strategy, when students simply choose the most preferred college in each period (denoted the straightforward strategy), the matching that is produced is the Student Optimal Stable Matching. Moreover, under imperfect information, students following the straightforward strategy is an Ordinal Perfect Bayesian Equilibrium. Based on data from 2016, we also provide evidence that, due to shortcomings which are absent in the modified version that we propose, the currently used mechanism in Brazil fails to assist the students with reliable information about the universities that they are able to attend, and are subject to manipulation via cutoffs, a new type of strategic behavior that is introduced by this family of iterative mechanisms and observed in the field.