IMPROVING POPULATION-SPECIFIC ALLELE FREQUENCY ESTIMATES BY ADAPTING SUPPLEMENTAL DATA: AN EMPIRICAL BAYES APPROACH

Estimation of the allele frequency at genetic markers is a key ingredient in biological and biomedical research, such as studies of human genetic variation or of the genetic etiology of heritable traits. As genetic data becomes increasingly available, investigators face a dilemma: when should data from other studies and population subgroups be pooled with the primary data? Pooling additional samples will generally reduce the variance of the frequency estimates; however, used inappropriately, pooled estimates can be severely biased due to population stratification. Because of this potential bias, most investigators avoid pooling, even for samples with the same ethnic background and residing on the same continent. Here, we propose an empirical Bayes approach for estimating allele frequencies of single nucleotide polymorphisms. This procedure adaptively incorporates genotypes from related samples, so that more similar samples have a greater influence on the estimates. In every example we have considered, our estimator achieves a mean squared error (MSE) that is smaller than either pooling or not, and sometimes substantially improves over both extremes. The bias introduced is small, as is shown by a simulation study that is carefully matched to a real data example. Our method is particularly useful when small groups of individuals are genotyped at a large number of markers, a situation we are likely to encounter in a genome-wide association study.     

Suppressing Asset Price Inflation: The Confederate Experience, 1861–1865

Confederate asset price stabilization policies appear to have increased the velocity of circulation and counterproductively channeled inflationary pressures into other areas of the economy. Three successive monetary reforms encouraged holders of Treasury notes to exchange these notes for bonds by imposing deadlines on their convertibility. We show that Confederate funding acts aimed at precipitating the conversion of currency into bonds did temporarily suppress currency depreciation. These acts also triggered upsurges in commodity prices, however, because note holders rushed to spend the currency before their exchange rights were reduced.     

Wer erbt Mehr? Erbschaften, Sozialstruktur und Alterssicherung

How do inheritances affect social structure, wealth formation, and provision for old age? Who benefits the most from inheritances? We analyse these questions based on the 2001 wave of the Socio-Economic Panel, which gives information on the deceased, and on the type, time, chance, and amount of the inheritance. Our findings confirm the theoretical hypotheses in general. Inheritance research is intergenerational research: most inheritances come from parents and benefit the recipients in the second half of their lives. However, the chances of receiving an inheritance and amounts inherited are distributed very unevenly. West Germans inherit significantly more frequently and larger amounts than East Germans due to the continuing effects of conditions in the former GDR. Foreigners have particularly low chances of receiving an inheritance. Thus, provision for old age through inheritance is limited mainly to specific groups of people. The most advantaged groups are the highly educated classes, which already receive higher (retirement) income.     

To File Or Not To File? Systemic Incentives, Corporate Control, and the Bankruptcy Decision

This research investigates the distinctions between bankrupt firms and equally leveraged firms that avoid bankruptcy. Building upon the systemic incentives of bankruptcy law, and specifically those applicable to Chapter 11 reorganizations, the study argues that the firm’s governance and capital structure characteristics moderate the relationship between the firm’s financial condition and the filing decision. The results of this study indicate that, contrary to agency theoretical predictions, firms with high levels of inside equity ownership and secured indebtedness file in poorer financial condition than peer firms with low levels of these variables. By contrast, firms with high levels of outside equity ownership and short-term indebtedness file when in relatively better financial condition.     

Transfer programs and aggregate household formations

The number of households in the United States increased by over fifty percent in the 1960s and 1970s, nearly double the rate of population growth. Part of the increase is explained by the movement of large cohort groups of the population into prime household-forming age categories, but higher headship rates also contribute. Age-specific headship rate increases result from non-demographic factors, and this paper focuses on the role of government transfer payment programs. Specifically considered are Social Security, Aid to Families with Dependent Children, and Food Stamps. These programs are found to have accounted for as many as 4 million net household formations between 1961 and 1984. The findings have implications for expected households formations in the 1990s.     

Uncertainty and Sensitivity Analysis in Assessment of the Thyroid Cancer Risk Related to Chernobyl Fallout in Eastern France

The increase in the thyroid cancer incidence in France observed over the last 20 years has raised public concern about its association with the 1986 nuclear power plant accident at Chernobyl. At the request of French authorities, a first study sought to quantify the possible risk of thyroid cancer associated with the Chernobyl fallout in France. This study suffered from two limitations. The first involved the lack of knowledge of spontaneous thyroid cancer incidence rates (in the absence of exposure), which was especially necessary to take their trends into account for projections over time; the second was the failure to consider the uncertainties. The aim of this article is to enhance the initial thyroid cancer risk assessment for the period 1991-2007 in the area of France most exposed to the fallout (i.e., eastern France) and thereby mitigate these limitations. We consider the changes over time in the incidence of spontaneous thyroid cancer and conduct both uncertainty and sensitivity analyses. The number of spontaneous thyroid cancers was estimated from French cancer registries on the basis of two scenarios: one with a constant incidence, the other using the trend observed. Thyroid doses were estimated from all available data about contamination in France from Chernobyl fallout. Results from a 1995 pooled analysis published by Ron et al. were used to determine the dose-response relation. Depending on the scenario, the number of spontaneous thyroid cancer cases ranges from 894 (90% CI: 869-920) to 1,716 (90% CI: 1,691-1,741). The number of excess thyroid cancer cases predicted ranges from 5 (90% UI: 1-15) to 63 (90% UI: 12-180). All of the assumptions underlying the thyroid cancer risk assessment are discussed.     

Scoring rules on dichotomous preferences

In this paper, we study individual incentives to report preferences truthfully for the special case when individuals have dichotomous preferences on the set of alternatives and preferences are aggregated in form of scoring rules. In particular, we show that (a) the Borda Count coincides with Approval Voting, (b) the Borda Count is the only strategy-proof scoring rule, and (c) if the size of the electorate is greater than three, then the dichotomous preference domain is the unique maximal rich domain under which the Borda Count is strategy-proof. I thank Jordi Massó for his supervision and his never-ending encouragement. Miguel-ángel Ballester showed me how to improve on earlier drafts of the paper. Salvador Barberà, Carmen Bevía, Bhaskar Dutta, Lars Ehlers, Alejandro Neme, Shmuel Nitzan and Yves Sprumont helped me a lot with their comments. All remaining errors are mine. This research was undertaken with support from the fellowship 2001FI 00451 of the Generalitat de Catalunya and from the research grant BEC2002-02130 of the Ministerio de Ciencia y Tecnología of Spain while I have been a graduate student at Universitat Autònoma de Barcelona.