The component structure of elderly population growth in the Netherlands: 1950–1980

While there is no doubt about the magnitude of the growth of older age groups in industrialized nations, its structural components are less well understood. This paper examines the roles played by cohort succession and mortality in the process for the Netherlands during the period 1950 to 1980. While the size of population aged 65 and over has increased for both males and females, increases in the size of succeeding cohorts explain all of the growth in the older male population. Reductions in mortality at the older old ages play a much greater role than do reductions at younger old ages; the latter reductions occur among females only.     

Distributional implications of equal sacrifice rules

A conclusive story can be made out of equal absolute and equal proportional sacrifice rules if only income after some poll tax of equal total revenue is taken as basis for distributional comparisons.     

OPTIMAL CALL SCHEDULING FOR A TELEPHONE SURVEY

Contacting a suitable respondent at home and securing the interviewis a significant component of the typical household telephonesurvey. An optimal calling schedule minimizes the number ofcallbacks required and thus conserves resources. This articlepresents an analysis of time-of-day and day-of-week effectson the probabilities of obtaining an answered outcome and aninterviewed outcome in a large national telephone survey ofadult males. The data presented indicate that, at least forthe survey population included in this study, the chances ofobtaining an answer and conducting an interview on the firstcall are much better on weekday evenings and on weekends thanthey are during weekday daytime hours. Moreover, there is someevidence to indicate that this finding also applies to secondcalls made to first-call no-answers, at least with regard tocontacting efforts. Time-of-day and/or day-of-week effects onfirst call outcomes appear to be generally consistent with respectto both contacting and interviewing, although Sunday has a decidedlyhigher interview response rate for answered calls than do theother calling periods analyzed.     

Three models of OPEC leadership and policy in the aftermath of Iran

Collapse of the Shah's regime has transformed Iran's attitude regarding oil production policy. The nature of OPEC leadership is changing as well. Three models examine the nature of this leadership inside OPEC: (1) the conventional price leadership model, (2) a model emphasizing a concept of egalitarian leadership, and (3) a team model composed of coalitions. The three models establish the limits within which OPEC leadership is exercised. A composite model drawing upon all three sets of results suggests that Saudi Arabia shapes cartel policy not by itself, but through a dominant coalition of states. For most of the period 1969–1978 this coalition has been stable. Following the unsettling changes of 1973, cooptation of Iran into the dominant coalition in 1974 was an important step in achieving a new level of stability. But during the turbulence of regime transformation in Iran, the nature of the governing coalition appears to have changed. One consequence may be that in the future Saudi Arabia will yield more willingly to arguments heard within OPEC on behalf of upwards price pressure, especially in an atmosphere of growing political isolation and overall tight supply.     

Biological Markers of Environmental and Ecological Contamination: An Overview

An approach, using biomarkers (biological responses) for assessing the biological and ecological significance of contaminants present in the environment is described. Living organisms integrate exposure to contaminants in their environment and respond in some measurable and predictable way. Responses are observed at several levels of biological organization from the biomolecular level, where pollutants can cause damage to critical cellular macromolecules and elicit defensive strategies such as detoxication and repair mechanisms, to the organismal level, where severe disturbances are manifested as impairment in growth, reproduction, developmental abnormalities, or decreased survival. Biomarkers can provide not only evidence of exposure to a broad spectrum of anthropogenic chemicals, but also a temporally integrated measure of bioavailable contaminant levels. A suite of biomarkers are evaluated over time to determine the magnitude of the problem and possible consequences. Relationships between biomarker response and adverse ecological effects are determined from estimates of animal health and population structure.     

Estimation of the mutagenic potency of environmental chemicals using short-term bioassay

The Ames Salmonella test is a widely used bioassay method for assessing the mutagenic potency of a potential carcinogen. The test is quick and reliable, and exploits the correlation that exists between mutagenic potential and carcinogenic potential. The data for this case study came from an international study involving 20 laboratories in nine countries. The laboratories participated in a designed experiment in which substances (complex chemical mixtures of the type encountered in the environment) were evaluated for mutagenicity using the Ames test. A stringent protocol was followed. The study's principal aim was to investigate intra- and inter-laboratory variation in test results. The data consist of counts of revertant Salmonella colonies at each of six dose levels of a substance. The data were obtained for each of five test substances from each participating laboratory. The bioassays were carried out according to a prescribed factorial experimental design. Three sets of analysts participated in this case study. They were asked to model the dose-response relationship for two substances, to develop an index of the strength of the relationship, and to assess intra- and inter-laboratory variation in bioassay results.     

An analysis of variables affecting length of stay in foster care

The purpose of this paper was to find out whether the relationship between type of contact with agency and/or child in foster care and average number of contacts over time makes any difference in length of stay in foster care. Four types of contacts were examined: Family—Agency, Family Initiated—Agency, Social Worker—Initiated, and Family—Child. Results indicated that there were critical numbers for each contact type found to be statistically significant that would tend to reduce the length of the child's stay in foster care. The importance of contact during the first month of placement was emphasized.