Who Lives Near Coke Plants and Oil Refineries? An Exploration of the Environmental Inequity Hypothesis

Facility-specific information on pollution was obtained for 36 coke plants and 46 oil refineries in the United States and matched with information on populations surrounding these 82 facilities. These data were analyzed to determine whether environmental inequities were present, whether they were more economic or racial in nature, and whether the racial composition of nearby communities has changed significantly since plants began operations.The Census tracts near coke plants have a disproportionate share of poor and nonwhite residents. Multivariate analyses suggest that existing inequities are primarily economic in nature. The findings for oil refineries are not strongly supportive of the environmental inequity hypothesis. Rank ordering of facilities by race, poverty, and pollution produces limited (although not consistent) evidence that the more risky facilities tend to be operating in communities with above-median proportions of nonwhite residents (near coke plants) and Hispanic residents (near oil refineries). Over time, the racial makeup of many communities near facilities has changed significantly, particularly in the case of coke plants sited in the early 1900s. Further risk-oriented studies of multiple manufacturing facilities in various industrial sectors of the economy are recommended.The authors are all affiliated with the Harvard Center for Risk Analysis     

Interstate migration of the US poverty population: Immigration “pushes” and welfare magnet “pulls”

This study evaluates the social and demographic structure of poverty migration during the 1985–90 period based on an analysis of recent census data. Particular attention is given to the roles of two policy-relevant factors that are proposed to be linked to poverty migration. The first of these is the role of immigration from abroad and its effect on the net out-migration of longer-term residents with below-poverty incomes, from States receiving the highest volume of immigrants. Such a response, it is argued, could result from job competition or other economic and social costs associated with immigration. The second involves the poverty population magnet effect associated with State welfare benefits (AFDC and Food Stamp payments) which has come under renewed scrutiny in light of the impending reform of the federal welfare program. The impact of both of these factors on interstate poverty migration is evaluated in a broader context that takes cognizance of other sociodemographic subgroups, and State-level attributes that are known to be relevant in explaining internal migration. This research employs an exceptionally rich data base of aggregate migration flows, specially tabulated from the full migration sample of the 1990 US census (based on the residence 5 years ago question). It also employs an analysis technique, the nested logit model, which identifies separately the push and pull effects of immigration, welfare benefits, and other State attributes on the migration process. Our findings are fairly clear. The high volume of immigration to selected US Statesdoes affect a selective out-migration of the poverty population, which is stronger for whites, Blacks and other non-Asian minorities as well as the least-educated. These results are consistent with arguments that internal migrants are responding to labor market competition from similarly educated immigrants. Moreover, we found that the impact of immigration occurs primarily as a push rather than a reduced pull. In contrast, State welfare benefits exert only minimal effects on the interstate migration of the poverty population—either as pulls or pushes, although some demographic segments of that population are more prone to respond than others. In addition to these findings, our results reveal the strong impact that a State's racial and ethnic composition exerts in both retaining and attracting migrants of like race and ethnic groups. This suggests the potential for a greater cross-state division in the US poverty population, by race and ethnic status.Data Used: 1990 US census tabulations of full migration (residence 5 years ago) sample. Note: Detailed 1990 census statistics on migration of the poverty and nonpoverty populations for individual states can be found in: William H. Frey Immigration and Internal Migration for US States: 1990 Census Findings by Poverty Status and Race, Population Studies CenterResearch Report No. 94-320.This research is supported by the University of Wisconsin Institute for Research on Poverty Small Grants Program and by NICHD grant No. R01 HD29725. The migration data for this paper were prepared at the Population Studies Center, University of Michigan from 1990 US Census files. The authors acknowledge Cathy Sun for computer programming assistance, and Ron Lue-Sang for preparing maps and graphics.     

On the generalized constrained longest common subsequence problems

We investigate four variants of the longest common subsequence problem. Given two sequences X, Y and a constrained pattern P of lengths m, n, and ρ, respectively, the generalized constrained longest common subsequence (GC-LCS) problems are to find a longest common subsequence of X and Y including (or excluding) P as a subsequence (or substring). We propose new dynamic programming algorithms for solving the GC-LCS problems in O(mn ρ) time. We also consider the case where the number of constrained patterns is arbitrary.     

Gender differences in the relationship between walking activity and sleep disturbance among community-dwelling older adult with diabetes in Taiwan

This study explored the gender differences in the relationship between walking activity and sleep disturbances. A cross-sectional study of 201 community-dwelling older adults with diabetes was conducted in southern Taiwan. Using the Taiwanese version of the International Physical Activity Questionnaire, self-administered short version (IPAQ-SS), information on physical activity and sleep disturbance conditions was collected. Among older female adults with diabetes, 54.2% reported sleep disturbance significantly higher than males (38.1%). Logistic regression analysis suggested that for women, in addition to the active group, older adults in the low-active, high-walking group exhibited a significantly lower rate of sleep disturbance than did those who walked less.     

Estimation and selection in linear mixed models with missing data under compound symmetric structure

It is quite appealing to extend existing theories in classical linear models to correlated responses where linear mixed-effects models are utilized and the dependency in the data is modeled by random effects. In the mixed modeling framework, missing values occur naturally due to dropouts or non-responses, which is frequently encountered when dealing with real data. Motivated by such problems, we aim to investigate the estimation and model selection performance in linear mixed models when missing data are present. Inspired by the property of the indicator function for missingness and its relation to missing rates, we propose an approach that records missingness in an indicator-based matrix and derive the likelihood-based estimators for all parameters involved in the linear mixed-effects models. Based on the proposed method for estimation, we explore the relationship between estimation and selection behavior over missing rates. Simulations and a real data application are conducted for illustrating the effectiveness of the proposed method in selecting the most appropriate model and in estimating parameters.     

The dependence of marriage migrations in Japan on personal factors and ecological variables

Marriage is an important migration‐inducing life‐cycle event. This paper uses a nested logit model to explain the interprefectural migration behaviors at marriage by personal factors and prefectural attributes, based on the micro data of the 1986 national migration survey of Japan. Before marriage, each person is considered a potential migrant making a two‐level decision: (1) to stay or depart and (2) to choose a destination. The main findings are as follows.

Destination choice propensities were affected by such attributes of potential destination as income (+), employment growth (+), distance (‐), contiguity (+), and linguistic similarity (+). Non‐natives appeared to be less sensitive to the attraction of economic opportunities. Personal factors were less important than prefectural attributes in affecting destination choice propensities.

Departure propensities were affected by not only such attributes of origin prefecture as income (‐), employment growth (‐), and population density (+) but also the “inclusive variable”; (+), which reflected the attractiveness of the rest of the system. Despite being strongly emphasized in the literature, sibling status was less important than gender, nativity and education in affecting departure propensities. Personal factors were much more important than prefectural attributes in determining the departure propensities.     

F_{3}-domination problem of graphs

Given a graph \(G\) and a set \(S\subseteq V(G),\) a vertex \(v\) is said to be \(F_{3}\) -dominated by a vertex \(w\) in \(S\) if either \(v=w,\) or \(v\notin S\) and there exists a vertex \(u\) in \(V(G)-S\) such that \(P:wuv\) is a path in \(G\) . A set \(S\subseteq V(G)\) is an \(F_{3}\) -dominating set of \(G\) if every vertex \(v\) is \(F_{3}\) -dominated by a vertex \(w\) in \(S.\) The \(F_{3}\) -domination number of \(G\) , denoted by \(\gamma _{F_{3}}(G)\) , is the minimum cardinality of an \(F_{3}\) -dominating set of \(G\) . In this paper, we study the \(F_{3}\) -domination of Cartesian product of graphs, and give formulas to compute the \(F_{3}\) -domination number of \(P_{m}\times P_{n}\) and \(P_{m}\times C_{n}\) for special \(m,n.\)      

On kernel estimators of density ratio

Let f(x) and g(x) denote two probability density functions and g(x)≠0. There are two ways to estimate the density ratio f(x)/g(x). One is to estimate f(x) and g(x) first and then the ratio, the other is to estimate f(x)/g(x) directly. In this paper, we derive asymptotic mean square errors and central limit theorems for both estimators.     

Maximum likelihood estimation in hazard rate models with a change-point

The problem of estimation of parameters in hazard rate models with a change-point is considered. An interesting feature of this problem is that the likelihood function is unbounded. A maximum likelihood estimator of the change-point subject to a natural constraint is proposed, which is shown to be consistent.The limiting distributions are also derived.     

Location of adult children as an attraction for black and white elderly return and onward migrants in the United States: Application of a three-level nested logit model with census data

This article assesses the influence of the location of adult children on the 1985-90 interstate migration of black and white elderly "nonnatives" (i.e., those whose state of residence in 1985 was different from their state of birth) in the United States, based on the application of a three-level nested logit model with 1990 census data. The model accounts for (1) the choice between departing and staying put, (2) the choice between return and onward migration, and (3) the choice of a specific destination. The main findings are as follows. First, elderly nonnatives were strongly attracted by the location of their adult children when they made their migration decisions at all levels of the choice framework, and this attraction was stronger for the widowed than for those of other marital statuses. This finding can be taken as empirical support for Eugene Litwak's theory of the modified extended family. Second, in the return/onward and destination choice processes, the attraction of the location of adult children was found to be stronger for whites than for blacks. This finding is consistent with the finding of Hogan et al. (1993) that whites had stronger inter-generational connections than did blacks.