Have Americans' Attitudes Become More Polarized?—An Update*

Objective. I examine polarization in public opinion using the method of DiMaggio, Evans, and Bryson (DEB) (1996), but go further than DEB by using newly available years of survey data. Method. Like DEB, I derive aggregate distributional parameters for social groups in each year of the surveys, and then regress the year of the surveys on each parameter. Results. As in DEB's original paper, there is little evidence of general polarization in attitudes between the early 1970s and today. However, while DEB found some evidence that polarization in the public may be the result of polarization in our political system, with the additional years of data this conclusion is inescapable. Conclusions. Although political scientists have recently found polarization among our elected officials on economic issues, it seems clear that members of the public who identify with the partisan labels of our political system are becoming polarized on moral issues.     

Factors Associated with the Enactment of Safety Belt and Motorcycle Helmet Laws

It has been shown that road safety laws, such as motorcycle helmet and safety belt laws, have a significant effect in reducing road fatalities. Although an expanding body of literature has documented the effects of these laws on road safety, it remains unclear which factors influence the likelihood that these laws are enacted. This study attempts to identify the factors that influence the decision to enact safety belt and motorcycle helmet laws. Using panel data from 31 countries between 1963 and 2002, our results reveal that increased democracy, education level, per capita income, political stability, and more equitable income distribution within a country are associated with the enactment of road safety laws.     

Bayesian ikference procedures derived via the concept of relative surprise

We consider the problem of deriving Bayesian inference procedures via the concept of relative surprise. The mathematical concept of surprise has been developed by I.J. Good in a long sequence of papers. We make a modification to this development that permits the avoidance of a serious defect; namely, the change of variable problem. We apply relative surprise to the development of estimation, hypothesis testing and model checking procedures. Important advantages of the relative surprise approach to inference include the lack of dependence on a particular loss function and complete freedom to the statistician in the choice of prior for hypothesis testing problems. Links are established with common Bayesian inference procedures such as highest posterior density regions, modal estimates and Bayes factors. From a practical perspective new inference procedures arise that possess good properties.     

Mathematical modeling in sociology: An exemplar (1)

This paper describes the method of differential equation modeling. To illustrate its application in sociology, a theory of the contribution of income to occupational prestige is developed and tested. The importance of theoretical foundations and inference therefrom is then discussed with a view to providing a model for teaching and the initiation of research.     

Comparison of Four Bootstrap‐Based Interval Estimators of Species Occupancy and Detection Probabilities

Site occupancy, as estimated by the probability of presence, is used for monitoring species populations. However, the detection of species at individual sites is often subject to errors. In order to accurately estimate occupancy we must simultaneously account for imperfect detectability by estimating the probability of detection. The problem with estimating occupancy arises from not knowing whether a nondetection occurred at an occupied site due to imperfect detectability (sampling zeros), or the nondetection resulting from an unoccupied site (fixed zeros). We evaluated the performance of the basic, normal approximation, studentised and percentile methods for approximating confidence limits for occupancy and detection of species. Using coverage and average interval width, we demonstrated that the studentised estimator was generally superior to the others, except when a small sample of sites are selected. Under this circumstance and when calculating limits for detection, no estimator produced reliable results. The experimental factors we considered include: (i) number of sites; (ii) number of survey occasions; (iii) probabilities of presence (occupancy) and detection; and (iv) overdispersion in the capture matrix. Similar conclusions were reached both for the simulated studies and a case study. Overall, estimation near the boundaries of the probability of occupancy and detectability was difficult.     

Permutation tests for the independence of a scalar and a unit vector

The problem of testing the independence of a scalar and a unit vector is re-examined in the context of a specific scientific problem which is described in Section 1. Several alternatives to the Jupp-Mardia (1980) statistic are suggested. The null distributions of all the statistics are discussed under permutations.     

Accidental fatalities in transport

Summary. The paper considers accidents on the different modes of transport. Accidents have many kinds of unwanted effects, though the paper focuses on just one: accidental fatalities. The paper reviews the main official sources of accident data and considers the use of past accident data. It then offers data and discussion on the numbers of accidental fatalities per year, passenger fatality rates, major accidents and the fatalities imposed by transport on third parties. The paper concludes with a brief discussion of communicating these results.     

Migration and health

Investigation of migration and health often forces us to acknowledge that the types of migration (international, internal, and residential) interact with each other as well as other population parameters such as the age/sex structure, sexual activity, fertility, mortality, and family structure. Research on migration is often obscured by these interactions. In fact, the adoption of a health perspective in the design of migration research represents a substantial improvement over traditional approaches that are based on distinctions among the various types of population movement. This is because a health perspective treats population movement as a dynamic process by which individuals are related to specific locations by reason of their participation in human networks. In other words, migration is regarded as a human process rather than a discrete event, and accordingly, it becomes less important to describe the individual's involvement with human networks and the institutions sustaining them. The use of a health perspective in migration research often calls our attention to the ways in which the types of migration are interconnected. For example, a migrant from Mexico might exhibit considerable internal mobility and may circulate between Mexico might exhibit considerable internal mobility and may circulate between Mexico and the US over several years until he develops enough contacts in the US to settle in a particular community in which his personal contact with human networks and place-specific institutions are conducive to settlement. Through him, family members may attach to the community. In the process, they all encounter health risks, make demands on the health care system, change the demographic/health characteristics of both sending and receiving places, sometimes act as transmitting agents of disease to those with whom they interact and, undergo changes in their levels of personal development and well-being. A research perspective that investigates these processes will consider all of the types of movement and characterize them as dynamic processes rather than as discrete events. The articles in this issue all touch on the ways in which migration can affect the health of migrants, and show the circle range of ways migration and health are interrelated. A special introductory note also suggests Acquired Immunodeficiency Syndrome (AIDS) should receive special attention in the study of this interrelationship. The uneven distribution of AIDS is heightening concern about the health implications for receiving countries.     

Future trends in world trade (A review of the Lima target)

In March 1975, the United Nations Industrial Development Organization held an important conference at Lima to discuss ways of speeding up the industrialization of developing countries. Various targets were formulated by the conference to achieve further growth in the developing areas of the world, which could have far-reaching implications not only for the developing countries, but also for the developed. The whole structure of world trade could be radically changed by the year 2000 and, as the authors of this article argue, the likely growth of various industries could be altered significantly over the next 25 years.