First Partial Differentiation by Computer with an Application to Categorical Data Analysis

A strategy is presented for producing code to evaluate first partial derivatives of a function f by computer. Advantage is taken of the capabilities that a compiler must have simply to bring about the evaluation of f. A bound kt on the time it should take to evaluate the partials of f is developed, where f takes time t to evaluate and k is independent of f. The benefits of the differentiation strategy for weighted least squares analysis of categorical data are discussed.     

Envisioning agricultural sustainability from field to plate: Comparing producer and consumer attitudes and practices toward ‘environmentally friendly’ food and farming in Washington State, USA

A substantial body of sociological research has examined the relationship between farmers’ environmental attitudes and their conservation behaviors, but little research has compared the attitudes of producers and consumers toward the environment with their behaviors or practices in support of sustainable agri-food systems. This paper addresses these shortcomings by analyzing the intersection between producer and consumer attitudes toward environmental sustainability with their actual practices, drawing data from focus group interviews and surveys with producers and consumers in Washington State, USA. We compare farmers’ attitudes toward several agricultural and environmental policies with their self-reported practices to examine whether support for environmental policies aligns with sustainable farming practices. For consumers, we investigate the relationship between their attitudes toward the same agricultural and environmental policy issues with their interest in purchasing food produced in an environmentally sustainable manner. Through our analyses, we find that consumers’ and producers’ practices are not always consistently correlated with their environmental attitudes, but that support for agricultural land preservation is one policy area in which the interests of producers and consumers intersect with their interest in sustainable farming and food. Findings from our individual and focus group interviews assist us in understanding the multiple, sometimes competing, factors that consumers and producers must weigh in making decisions about environmentally sustainable food and farming.     

A History of the Development of Craig's Theorem

Craig's theorem on the independence of quadratic forms in normal variates is traced from its first form, for iid standard normal variates, to the form for variates following an arbitrary nonsingular joint normal distribution. This article gives the main thrust of the development and makes recommendations on coverage of the theorem in courses and textbooks. The history of Craig's theorem is not a happy one. The authors of the earlier articles in the literature tended to make errors of a linear-algebraic nature. Authors of more recently published textbooks have given incorrect or misleadingly incomplete coverage of Craig's theorem and its proof.     

The effect of climate on migration: United States, 1995–2000

This paper examines the effect of climate on migration. We examine whether climate is an influential factor in internal migration. We assume that most persons tend to avoid exposure to bitter and cold winters, and excessively hot and humid summers, preferring climates between these extremes. When engaging in-migration decision-making, therefore, to the extent possible, considerations involving climate are believed to be brought into the calculus. There is a very limited demographic literature on the effects of climate on migration.In this paper, we undertake an aggregate-based analysis of the effect of climate on migration. We examine this relationship among the 50 states of the United States. We focus attention on the varying effects of climate on three migration measures for the 1995–2000 time period, namely, in-migration, out-migration, and net migration. We next evaluate the effect of climate on migration in the context of a broad application of human ecology. Here climate, a manifestation of the physical environment, is measured with three major independent variables. The other ecological predictors pertaining to organization, population, technology, and the social environment are used as controls. This enables us to examine the effects of climate on migration in the context of competing ecological hypotheses.     

Analysis of tidal data via the blockwise bootstrap

We analyze tidal data from Port Mansfield, TX, using Kunsch's blockwise bootstrap in the regression setting. In particular, we estimate the variability of parameter estimates in a harmonic analysis via block subsampling of residuals from a least-squares fit. We see that naive least-squares variance estimates can be either too large or too small, depending on the strength of correlation and the design matrix. We argue that the block bootstrap is a simple, omnibus method of accounting for correlation in a regression model with correlated errors.     

Welfare Reform's Impact on Homelessness

As the most dramatic shift in welfare policy occurs since its inception in 1935, it is imperative to examine potential impacts on homelessness. This paper describes changes in homelessness and welfare policy, assesses potential effects of the Personal Responsibility and Work Opportunity Reconciliation Act of 1996, and addresses public policy issues stemming from these changes. Of utmost concern are the continuing growth in female-headed families among the ranks of the homeless and a decline in affordable housing units. Welfare reform has already reduced the numbers of persons on welfare rolls, but it remains unclear as to whether the situation of low-income and homeless female-headed families will become better or worse.