Sample Selection in Models of Academic Performance

This article shows how admission and enrollment processes affect the interpretation of simple validation studies of academic performance. In a competitive market for students, optimal behavior of admissions committees and applicants drives the simple correlation between test scores and performance toward zero, regardless of the relationship in the population of prospective students. Data from our university's MBA program support the prediction that applicants exhibit a higher correlation between test scores and undergraduate GPAs than do current students. This suggests that standard validation studies will understate the importance of GMAT scores in predicting performance of potential MBA students. (JEL C24 , I121 , C52 )     

How race affects dismissals of college football coaches

We employ a discretetime hazard model and a Blinder-decomposition approach to explore the possibility of racial discrimination in the dismissal and retention of college football coaches by university administrations. A rich data set consisting of 81 institutions over an 11-year period (1990–2000) that contains, in addition to a coach's race, variables on cumulative winning records, annual on-the-field improvements, and pre-/post-season game participation by institutions and their coaches is employed. Our study finds that black coaches, on average, face a dismissal probability that is 9.6 percentage points below that of their nonblack counterparts, ceteris paribus, suggesting that black head coaches may be the beneficiaries of favorable treatment by university administrators. Such a result likely stems from universities ' approach to social concerns involving race and gender issues. This finding also fits a construct that considers workplace discrimination as multi-dimensional. For example, black representation in the college football coaching ranks may be disproportionately low, possibly as a result of discrimination. However, once hired, black coaches are given more time to succeed than nonblacks, other things constant.     

School-Choice Stories: The Role of Culture

This article uses data from in-depth interviews conducted with the parents of a sample of 88 ninth-grade students from public, private, Catholic, and Christian high schools in two different suburban communities. This research investigates the ways in which parents understand education and how they make sense of schooling options for their children. It shows both how families who choose schools make the selection among various alternatives and why some families seem not to choose schools. This research finds that the financial and information resources of families are not enough in and of themselves to explain school-choice behavior. While these resources are indeed used by families as they make school choices, such measures do not capture the cultural dimension of school choice. In this context culture is understood as the lens through which people make sense of the social world. The decision to activate resources and the direction in which those resources will be activated are mediated by culture. In particular, as these school-choice stories show, the school-choice decision is influenced by the past educational experiences of the parents and by their religious faith.     

Characterizing Environmental Harm: Developments in an Approach to Strategic Risk Assessment and Risk Management

Environmental policymakers and regulators are often in the position of having to prioritize their actions across a diverse range of environmental pressures to secure environmental protection and improvements. Information on environmental issues to inform this type of strategic analysis can be disparate; it may be too voluminous or even absent. Data on a range of issues are rarely presented in a common format that allows easy analysis and comparison. Nevertheless, judgments are required on the significance of various environmental pressures and on the inherent uncertainties to inform strategic assessments such as “state of the environment” reports. How can decisionmakers go about this type of strategic and comparative risk analysis? In an attempt to provide practical tools for the analysis of environmental risks at a strategic level, the Environment Agency of England and Wales has conducted a program of developmental research on strategic risk assessment since 1996. The tools developed under this program use the concept of “environmental harm” as a common metric, viewed from technical, social, and economic perspectives, to analyze impacts from a range of environmental pressures. Critical to an informed debate on the relative importance of these perspectives is an understanding and analysis of the various characteristics of harm (spatial and temporal extent, reversibility, latency, etc.) and of the social response to actual or potential environmental harm from a range of hazards. Recent developments in our approach, described herein, allow a presentation of the analysis in a structured fashion so as to better inform risk‐management decisions.     

Modeling Growth and Reduction of Microorganisms in Foods as Functions of Temperature and Time

Food safety objectives (FSOs) are established in order to minimize the risk of foodborne illnesses to consumers, but these have not yet been incorporated into regulatory policy. An FSO states the maximum frequency and/or concentration of a microbiological hazard in a food at the time of consumption that provides an acceptable level of protection to the public and leads to a performance criterion for industry. However, in order to be implemented as a regulation, this criterion has to be achievable by the affected industry. In order to determine an FSO, the steps to produce and store that food need to be known, especially where they have an impact on contamination, growth, and destruction. This article uses existing models for growth of Listeria monocytogenes in conjunction with calculations of FSOs to approximate the outcome of more than one introduction of the foodborne organism throughout the food-processing path from the farm to the consumer. Most models for the growth and reduction of foodborne illnesses are logarithmic in nature, which fits the nature of the growth of microorganisms, spanning many orders of magnitude. However, these logarithmic models are normally limited to a single introduction step and a single reduction step. The model presented as part of this research addresses more than one introduction of food contamination, each of which can be separated by a substantial amount of time. The advantage of treating the problem this way is the accommodation of multiple introductions of foodborne pathogens over a range of time durations and conditions.     

Addressing Nonlinearity in the Exposure-Response Relationship for a Genotoxic Carcinogen: Cancer Potency Estimates for Ethylene Oxide

Ethylene oxide (EO) has been identified as a carcinogen in laboratory animals. Although the precise mechanism of action is not known, tumors in animals exposed to EO are presumed to result from its genotoxicity. The overall weight of evidence for carcinogenicity from a large body of epidemiological data in the published literature remains limited. There is some evidence for an association between EO exposure and lympho/hematopoietic cancer mortality. Of these cancers, the evidence provided by two large cohorts with the longest follow-up is most consistent for leukemia. Together with what is known about human leukemia and EO at the molecular level, there is a body of evidence that supports a plausible mode of action for EO as a potential leukemogen. Based on a consideration of the mode of action, the events leading from EO exposure to the development of leukemia (and therefore risk) are expected to be proportional to the square of the dose. In support of this hypothesis, a quadratic dose-response model provided the best overall fit to the epidemiology data in the range of observation. Cancer dose-response assessments based on human and animal data are presented using three different assumptions for extrapolating to low doses: (1) risk is linearly proportionate to dose; (2) there is no appreciable risk at low doses (margin-of-exposure or reference dose approach); and (3) risk below the point of departure continues to be proportionate to the square of the dose. The weight of evidence for EO supports the use of a nonlinear assessment. Therefore, exposures to concentrations below 37 microg/m3 are not likely to pose an appreciable risk of leukemia in human populations. However, if quantitative estimates of risk at low doses are desired and the mode of action for EO is considered, these risks are best quantified using the quadratic estimates of cancer potency, which are approximately 3.2- to 32-fold lower, using alternative points of departure, than the linear estimates of cancer potency for EO. An approach is described for linking the selection of an appropriate point of departure to the confidence in the proposed mode of action. Despite high confidence in the proposed mode of action, a small linear component for the dose-response relationship at low concentrations cannot be ruled out conclusively. Accordingly, a unit risk value of 4.5 x 10(-8) (microg/m3)(-1) was derived for EO, with a range of unit risk values of 1.4 x 10(-8) to 1.4 x 10(-7) (microg/m3)(-1) reflecting the uncertainty associated with a theoretical linear term at low concentrations.     

The Multicultural Welfare State: International Experience and North American Narratives

Contemporary debates are increasingly pessimistic about the impact of ethnic diversity on support for the welfare state. A growing number of analysts argue that greater ethnic diversity in Western democracies is weakening public support for redistribution, and that this underlying tension is exacerbated by the adoption of robust multiculturalism policies. The purpose of this essay is to summarize early findings from several studies that bear on the questions at the heart of such debates. These studies analyse the implications of immigration and multiculturalism policies for the welfare state across OECD countries, and also focus more closely on the experience of two distinctively multicultural countries, the United States and Canada. The evidence points to more complex relationships than often assumed. OECD countries with large foreign‐born populations have not had more difficulty in sustaining their welfare states than other countries. The extent of change does seem to matter, however, as countries in which immigrant communities grew rapidly between 1970 and the late 1990s did experience lower rates of growth in social spending. But despite the warnings of some critics, robust multiculturalism policies do not systematically exacerbate this tension. Moreover, the United States and Canada reflect different patterns. In the US racial diversity does weaken support for redistribution; but Canadian experience suggests that immigration, multiculturalism policies and redistribution can represent a stable political equilibrium. These contrasting narratives from North America stand as a warning against premature conclusions based on the US experience alone. There is no inevitability at work, and policy choices do seem to matter.     

Older Workers: Who are the working poor in the U.S.?

With data from the 2000 Health and Retirement Study (HRS), the purpose of this study was to provide a profile of older workers who live poverty, and to compare the demographic, financial, employment, and health attributes of such individuals to similar persons not living in poverty. This study found that 3.5% of employed individuals between the ages of 51 and 61 belonged to the class of working poor. The results of the multivariate logistic regression analyses indicated that the older working poor were more likely to be non-White, less educated, non-married, and had lower levels of net worth than the working non-poor. They were more likely to be employed part time and were less likely to be covered by employee-sponsored health insurance.     

The Timing of Entry Into Fatherhood in Young, At-Risk Men

Timing of first fatherhood was examined in a sample of 206 at-risk, predominantly White men, followed prospectively for 17 years. An event history analysis was used to test a model wherein antisocial behavior, the contextual and familial factors that may contribute to the development of antisocial behavior, and common correlates of such behavior, including academic failure, substance use, and early initiation of sexual behaviors, lead both directly and indirectly to an early transition to fatherhood. Having a mother who was younger at first birth, low family SES, poor academic skills, failure to use condoms, and being in a cohabitating or marital relationship predicted entry into fatherhood. Implications of the findings for prevention of and intervention with early fathering are discussed.