A dominant strategy, double clock auction with estimation-based tatonnement

The price mechanism is fundamental to economics but difficult to reconcile with incentive compatibility and individual rationality. We introduce a double clock auction for a homogeneous good market with multidimensional private information and multiunit traders that is deficit‐free, ex post individually rational, constrained efficient, and makes sincere bidding a dominant strategy equilibrium. Under a weak dependence and an identifiability condition, our double clock auction is also asymptotically efficient. Asymptotic efficiency is achieved by estimating demand and supply using information from the bids of traders that have dropped out and following a tâtonnement process that adjusts the clock prices based on the estimates

Topological Order and Quantum Criticality

In this chapter we discuss aspects of the quantum critical behavior that occurs at a quantum phase transition separating a topological phase from a conventionally ordered one. We concentrate on a family of quantum lattice models, namely certain deformations of the toric code model, that exhibit continuous quantum phase transitions. One such deformation leads to a Lorentz-invariant transition in the 3D Ising universality class. An alternative deformation gives rise to a so-called conformal quantum critical point where equal-time correlations become conformally invariant and can be related to those of the 2D Ising model. We study the behavior of several physical observables, such as non-local operators and entanglement entropies, that can be used to characterize these quantum phase transitions. Finally, we briefly consider the role of thermal fluctuations and related phase transitions, before closing with a short overview of field theoretical descriptions of these quantum critical points.Comment: 24 pages, 7 figures, chapter of the book "Understanding Quantum Phase Transitions", edited by Lincoln D. Carr (CRC Press / Taylor and Francis, 2010); v2: updated reference

What Drove First Year Premiums in Stand-Alone Medicare Drug Plans?

Medicare's Part D offers heavily subsidized new drug coverage to 22.5 million seniors to date, of whom 16.5 million are in stand-alone drug plans (Department of Health and Human Services, 2006). The government delegated the delivery of the benefit to private insurance companies arguing that market incentives would lead them to provide coverage at the lowest price possible. The massive entry of plans and the large variety of actuarial designs and formularies offered make it complicated to assess how insurers set premiums during this first year of the program. This paper presents the first econometric evidence on whether premiums in the stand-alone drug plan markets are driven by the relevant factors predicted by insurance theory. Using data gathered from the Centers for Medicare and Medicaid Services, we measure a plan's generosity as the simulated out of pocket payments for different sets of drugs. We also identify the listed full drug prices by each insurer and merge these with other plan and geographical characteristics to test predictions about how insurers set premiums. We find evidence that a) the number of insurers in a market is big enough such that it does not appear to influence premiums, b) the full drug prices listed appear to be reflected to some degree in the premiums charged c) plan characteristics such as the provision of extra coverage are reflected in higher premiums, but overall there is a weak relationship between premiums and simulated out of pocket payments for different sets of drugs d) the institutional setting and regional market characteristics affect the firms' bidding behavior and their resulting premiums. Insurers appear to have responded strongly to program incentives such as the automatic enrollment of dual Medicaid-Medicare beneficiaries into low cost plans. As data for 2007 are made available, it will be important to see if plans follow similar pricing strategies in subsequent years of this program.

The Welfare Impact of Reducing Choice in Medicare Part D: A Comparison of Two Regulation Strategies

Motivated by widely publicized concerns that there are “too many” plans, we structurally estimate (and validate) an equilibrium model of the Medicare Part D market to study the welfare impacts of two feasible, similar-sized approaches for reducing choice. One reduces the maximum number of firm offerings regionally; the other removes plans providing donut hole coverage – consumers’ most valued dimension. We find welfare losses are far smaller when coupled with elimination of a dimension of differentiation, as in the latter approach. We illustrate our findings’ relevance under current health care reforms, and consider the merits of instead imposing ex ante competition for entry.

The Welfare Impact of Reducing Choice in Medicare Part D: A Comparison of Two Regulation Strategies

Medicare’s prescription drug benefit (Part D) has been its largest expansion of benefits since 1965. Since the implementation of Part D, many regulatory proposals have been advanced in order to improve this government-created market. Among the most debated are proposals to limit the number of options, in response to concerns that there are “too many” plans. In this paper we study the welfare impact of two feasible approaches (of similar magnitude) toward limiting the number of Part D plans: reducing the maximum number of plans each firm can offer per region and removing plans that provide doughnut hole coverage. To this end, we propose and estimate a model of market equilibrium, which we later use to evaluate the impact of regulating down the number of Part D plans. Our counterfactuals provide an important assessment of the losses to consumers (and producers) resulting from government limitations on choice. These losses must be weighed against the widely discussed expected gains due to reduced search costs from limiting options. We find that the annual search costs should be at least two thirds of the average monthly premium in order to justify a regulation that allows only two plans per firm. However, this number would be substantially lower if the limitation in the number of plans is coupled with a decrease in product differentiation (e.g., by removing plans that cover the doughnut hole). For validation purposes, we also assess the impact of a recent major merger, and find that our model performs very well out of sample.Medicare Part D, regulation, number of plans, product differentiation, discrete choice

A dominant strategy, double clock auction with estimation-based tâtonnement

The price mechanism is fundamental to economics but difficult to reconcile with incentive compatibility. We introduce a double clock auction for a homogeneous good market with multi-dimensional private information and multi-unit traders that is deficit-free, ex post individually rational, constrained efficient, and makes sincere bidding a dominant strategy equilibrium. Under a weak dependence and an identifiability condition, our double clock auction is also asymptotically efficient. Asymptotic efficiency is achieved by estimating demand and supply using information from the bids of traders that have dropped out and following a tatonnement process that adjusts the clock prices based on the estimates

Control of polymorphism in coronene by the application of magnetic fields

Coronene, a polyaromatic hydrocarbon, has been crystallized for the first time in a different polymorph using a crystal growth method that utilizes magnetic fields to access a unit cell configuration that was hitherto unknown. Crystals grown in magnetic field of 1 T are larger, have a different appearance to those grown in zero field and retain their structure in ambient conditions. We identify the new form, beta-coronene, as the most stable at low temperatures. As a result of the new supramolecular configuration we report significantly altered electronic, optical and mechanical properties.Comment: 32 pages, 17 figure

A Simple(r) Tool For Examining Fixations

This short paper describes an update of A Simple Tool For Examining Fixations (ASTEF) developed for facilitating the examination of eye-tracking data and for computing a spatial statistics algorithm that has been validated as a measure of mental workload (namely, the Nearest Neighbor Index: NNI). The code is based on Matlab® 2013a and is currently distributed on the web as an open-source project. This implementation of ASTEF got rid of many functionalities included in the previous version that are not needed anymore considering the large availability of commercial and open-source software solutions for eye-tracking. That makes it very easy to compute the NNI on eye-tracking data without the hassle of learning complicated tools. The software also features an export function for creating the time series of the NNI values computed on each minute of the recording. This feature is crucial given that the spatial distribution of fixations must be used to test hypotheses about the time course of mental load

Satisfacción de necesidades básicas y su repercusión en el curso del desarrollo

This study aimed at the development of the Reading Subtest of the second edition of the School Performance Test (TDE-II). This study consisted in items selection, analysis by experts, and validation in which a sample of 661 students from the first to the ninth grades of Elementary School participated. The Subtest was divided in two versions: version A for students from the first to the fourth grades and version B for students from the fifth to ninth grades. Exploratory factor analysis indicated unidimensionality with one factor explaining 57% of the shared items variance for version A and 38% for version B. Item Response Theory analysis indicated appropriate levels of discrimination and difficulty for measuring the construct. Results suggest sources of validity in relation to test content, and internal structure. In terms of reliability, both versions covered the range of ability with high precision, thus suggesting that the Subtest presents good psychometric properties for reading evaluation.Este estudo teve como objetivo o desenvolvimento do Subteste de Leitura da segunda edição do Teste de Desempenho Escolar (TDE-II). Este estudo envolveu a seleção de itens, análise de juízes e a validação que contou com a participação de 661 estudantes de 1º a 9º ano do ensino fundamental. O subteste foi dividido em duas versões: a versão A para estudantes de 1º a 4º ano e a versão B para 5º a 9º ano. A análise fatorial exploratória indicou que ambas as versões são unidimensionais com um fator explicando 57% da versão A e um fator explicando 38% da variância compartilhada pelos itens da versão B. Análises via Teoria de Resposta ao Item indicou níveis de discriminação e dificuldade adequados para mensurar o construto. Os resultados revelaram evidências relacionadas ao conteúdo e à estrutura interna do teste. Em relação à fidedignidade, as versões do Subteste de Leitura cobrem de forma precisa as habilidades, sugerindo que o subteste apresenta boas propriedades psicométricas para avaliação da leitura.Este estudio tuvo como objetivo desarrollar el Sub-test de Lectura de la segunda edición del Test de Desempeño escolar (TDE-II). El estudio consistió en la selección de ítems, análisis de jueces y una validación que contó con la participación de 661 alumnos de primer a noveno año de Enseñanza Primaria. El Sub-test se dividió en dos versiones: la versión A para estudiantes de primer a cuarto año y la versión B para alumnos de quinto a noveno año. El análisis factorial exploratorio indicó que las dos versiones son unidimensionales con un factor explicando el 57% de la versión A y 38% de la varianza compartida por los ítems de la versión B. Análisis vía Teoría de Respuesta al Ítem (TRI) indicaron niveles de discriminación y dificultad adecuados para medir el constructo. Los resultados mostraron evidencias relacionadas a contenido y a estructura interna del test. Con relación a la fidedignidad, las versiones del Sub-test de Lectura abarcan de manera precisa las habilidades, sugiriendo que el Sub-test presenta buenas propiedades psicométricas para evaluación de la lectura