MALARIA IN THE AMERICAS: A RETROSPECTIVE ANALYSIS OF CHILDHOOD EXPOSURE

This study considers the malaria-eradication campaigns in the United States (circa 1920), and in Brazil, Colombia and Mexico (circa 1955) in order to measure how much childhood exposure to malaria depresses labor productivity. The campaigns began because of advances in health technology, which mitigates concerns about reverse causality. Malarious areas saw large drops in the disease thereafter. Relative to non-malarious areas, cohorts born after eradication had higher income as adults than the preceding generation. These changes coincided with childhood exposure to the campaigns rather than with preexisting trends.Malaria, returns to health, eradication campaigns

Joint segmentation of many aCGH profiles using fast group LARS

Array-Based Comparative Genomic Hybridization (aCGH) is a method used to search for genomic regions with copy numbers variations. For a given aCGH profile, one challenge is to accurately segment it into regions of constant copy number. Subjects sharing the same disease status, for example a type of cancer, often have aCGH profiles with similar copy number variations, due to duplications and deletions relevant to that particular disease. We introduce a constrained optimization algorithm that jointly segments aCGH profiles of many subjects. It simultaneously penalizes the amount of freedom the set of profiles have to jump from one level of constant copy number to another, at genomic locations known as breakpoints. We show that breakpoints shared by many different profiles tend to be found first by the algorithm, even in the presence of significant amounts of noise. The algorithm can be formulated as a group LARS problem. We propose an extremely fast way to find the solution path, i.e., a sequence of shared breakpoints in order of importance. For no extra cost the algorithm smoothes all of the aCGH profiles into piecewise-constant regions of equal copy number, giving low-dimensional versions of the original data. These can be shown for all profiles on a single graph, allowing for intuitive visual interpretation. Simulations and an implementation of the algorithm on bladder cancer aCGH profiles are provided

Age at Arrival, English Proficiency, and Social Assimilation Among U.S. Immigrants

Are U.S. immigrants' English proficiency and social outcomes the result of their cultural preferences, or of more fundamental constraints? Using 2000 Census microdata, we relate immigrants' marriage, fertility and residential location variables to their age at arrival in the U.S., and in particular whether that age fell within the "critical period" of language acquisition. We interpret the differences between younger and older arrivers as effects of English-language skills and construct an instrumental variable for English-language skills. Two-stage-least-squares estimates suggest that English proficiency increases the likelihood of divorce and intermarriage. It decreases fertility and, for some groups, ethnic enclave residence.

The group fused Lasso for multiple change-point detection

We present the group fused Lasso for detection of multiple change-points shared by a set of co-occurring one-dimensional signals. Change-points are detected by approximating the original signals with a constraint on the multidimensional total variation, leading to piecewise-constant approximations. Fast algorithms are proposed to solve the resulting optimization problems, either exactly or approximately. Conditions are given for consistency of both algorithms as the number of signals increases, and empirical evidence is provided to support the results on simulated and array comparative genomic hybridization data

The Statistical Performance of Collaborative Inference

The statistical analysis of massive and complex data sets will require the development of algorithms that depend on distributed computing and collaborative inference. Inspired by this, we propose a collaborative framework that aims to estimate the unknown mean $\theta$ of a random variable $X$. In the model we present, a certain number of calculation units, distributed across a communication network represented by a graph, participate in the estimation of $\theta$ by sequentially receiving independent data from $X$ while exchanging messages via a stochastic matrix $A$ defined over the graph. We give precise conditions on the matrix $A$ under which the statistical precision of the individual units is comparable to that of a (gold standard) virtual centralized estimate, even though each unit does not have access to all of the data. We show in particular the fundamental role played by both the non-trivial eigenvalues of $A$ and the Ramanujan class of expander graphs, which provide remarkable performance for moderate algorithmic cost

Portage: path dependence and increasing returns in U.S. history

The authors examine portage sites in the U.S. South, Mid-Atlantic, and Midwest, including those on the fall line, a geomorphologic feature in the southeastern U.S. marking the final rapids on rivers before the ocean. Historically, waterborne transport of goods required portage around the falls at these points, while some falls provided water power during early industrialization. These factors attracted commerce and manufacturing. Although these original advantages have long since been made obsolete, the authors document the continuing-and even increasing-importance of these portage sites over time. They interpret this finding in a model with path dependence arising from local increasing returns to scale.Geography ; Urban economics

The Effects of English Proficiency among Childhood Immigrants: Are Hispanics Different?

We test whether the effect of English proficiency differs between Hispanic and non-Hispanic immigrants. Using 2000 U.S. Census microdata on immigrants who arrived before age 15, we relate labor market, education, marriage, fertility and location of residence variables to their age at arrival in the U.S., and in particular whether that age fell within the "critical period" of language acquisition. We interpret the observed difference in outcomes between childhood immigrants who arrive during the critical period and those who arrive later (adjusted for non-language-related age-at-arrival effects using childhood immigrants from English-speaking countries) as an effect of English- language skills and construct an instrumental variable for English-language skills. We find that both Hispanics and nonHispanics exhibit lower English proficiency if they arrive after the critical period, but this drop in English proficiency is larger for Hispanics. The effect of English proficiency on earnings and education is nevertheless quite similar across groups, while some differences are seen for marriage, fertility, and location of residence outcomes. In particular, although higher English proficiency reduces (for both groups) the number of children and the propensity to be married, marry someone with the same birthplace or origin, and live in an "ethnic enclave," these effects are smaller for Hispanics.

Corporate Dollar Debt and Depreciations: Much Ado About Nothing?

Much has been written recently about the problems for emerging markets that might result from a mismatch between foreign-currency denominated liabilities and assets (or income flows) denominated in local currency. In particular, several models, developed in the aftermath of financial crises of the late 1990s, suggest that the expansion in the "peso" value of "dollar" liabilities resulting from a devaluation could, via a net worth effect, offset the expansionary competitiveness effect. Assessing which effect dominates is ultimately an empirical matter. In this vein, this paper constructs a new database with accounting information (including the currency composition of liabilities) for over 450 non-financial firms in five Latin American countries. The authors estimate, at the firm level, the reduced-form effect on investment of holding foreign-currency-denominated debt during an exchange-rate realignment. It is consistently found that, contrary to the predicted sign of the net-worth effect, firms holding more dollar debt do not invest less than their counterparts in the aftermath of a depreciation. The paper shows that this result is due to firms matching the currency denomination of their liabilities with the exchange-rate sensitivity of their profits. Because of this matching, the negative balance-sheet effects of a depreciation on firms holding dollar debt are offset by the larger competitiveness gains of these firms.

The Differences in spelling when practice utilizes a word processor versus writing by hand; parent perceptions

The purpose of this study was to investigate parent perceptions about how their children become successful spellers by asking about digital and hand written practice alignment with test taking. Thirty parents of children from the primary grades of school (1st to 4th grade) were sought as participants. There was no control for the type of school (e.g. private versus public). The materials of the study included a brief questionnaire developed from the literature that ask demographic information (age, grade, etc.) and specifics about spelling homework, spelling tests in school, and perceived benefits of types of practice for spelling success. The questionnaire was distributed electronically via social media. Data from the questionnaire was used to descriptively answer the specific questions of the study