Testing Evolutionary Hypotheses with Demographic Data

An ecological evolutionary viewpoint offers new perspectives on contemporary demographic problems in general and on population–environment issues in particular. In turn, rich and detailed human demographic data can help solve problems of interest in evolutionary theory. Such data have been analyzed in greatest detail in studies of traditional and historical societies. Evolutionary approaches using historical data go beyond small‐sample anthropological studies to the application of the evolutionary approach to large datasets, and illuminate important similarities between small‐scale traditional societies and large modern populations living in evolutionarily novel environments. This article provides a concise update of the breadth of questions and hypotheses of likely interest to demographers and others that evolutionary theorists address using a variety of traditional and historical datasets. It suggests opportunities for additional collaborative work between evolutionary theorists and historical demographers and highlights topics relevant to modern demography.     

Child and Youth Well-Being in the United States, 1975–1998: Some Findings from a New Index

Social Indicators Research - This paper addresses the following questions: Overall, on average, how did child and youthwell-being in the United States of Americachange in the last quarter of the...     

The Relationship between Subjective Well-being and Domain Satisfactions in South Africa

This paper examines the relationship between subjective well-being and domain satisfactions. In the past different models have been specified. The most commonly applied model is the bottom-up model in which domain satisfactions affect subjective well-being. The more recent top-down model suggests a reversed relationship. Finally there is the supposition that the correlations between these variables can be spurious due to the effect of personality characteristics. Empirical research has shown that different models are found for different domains and in different countries. Focussing on the effects of the domain satisfactions of finances, housing and social contacts it has been found that subjective well-being is mainly affected by satisfaction with social contacts in Western developed countries and by satisfaction with finances in East European countries. The question we should like to answer in this study is whether a similar pattern obtains for the factors which influence subjective well-being among the different race groups in South Africa. Interestingly, coloured people and Asians did indeed show the expected effects but the groups with the most extreme living conditions did not. Evaluation of life circumstances by black and white South Africans was determined by expectations for the future rather than by current living conditions. This surprising result is discussed in the light of the political situation in South Africa.     

Some Cautions on the Measurement of User Information Satisfaction*

User information satisfaction (UIS) is important because of its potential effects on MIS department goals, quality of user work life, and extent of voluntary usage of systems. Reliable measurement of UIS is important for providing evaluative information for both researchers and practitioners. This study used 92 managers and executives as subjects to compare the test/retest reliability of a widely used, 13-scale UIS instrument together with four summary questions under experimental and control conditions. The summary questions behaved more reliably than the detailed questions for all groups, perhaps because of problems with scale units and origins and with item heterogeneity. This suggests that researchers need more reliable measures of UIS and that practitioners need to exercise caution when collecting and interpreting UIS scores.     

Efficient Heuristics for MRP Lot Sizing with Variable Production/Purchasing Costs*

Two heuristics based on branch and bound (B&B) are developed to solve closed-loop material requirements planning (MRP) lot-sizing problems that have general product structures and variable costs. A “look ahead method'’(LAM) heuristic allows for variable production/purchasing costs and uses a single-level B&B procedure to rapidly improve lower bound values; thus, LAM efficiently uses computer-storage capacity and allows solution of larger problems. The “total average modification'’(TAM) heuristic uses B&B, applied level by level, and modified setup and carrying costs to solve the variable production/purchasing costs MRP lot-sizing problem. LAM and TAM are tested on problems and compared to heuristics in the literature. TAM may be used to solve large MRP lot-sizing problems encountered in practice.     

Lowering Inventory Systems Costs by Using Regression-Derived Estimators of Demand Variability*

Scientific techniques for inventory management typically are applied to systems containing many items. Such techniques require an estimation of the demand variance (and mean) of each item from historical data. This research demonstrates a significant potential for improvement in system cost performance from using least-squares regression fits of a variance-to-mean functional relation instead of the standard statistical variance estimate. Even when there is a moderate degree of heterogeneity among items and when the form of the variance-to-mean relation is misspecified, substantial cost savings may be realized. The cost of statistical uncertainty may be reduced by half. The research also provides evidence that system cost is fairly insensitive to the number of items used to fit the regression. This paper provides the underlying reason why a regression-derived variance estimator yields lower cost: it is less variable than the usual individual item variance estimator.     

A Warning Zone Method for the Multiperiod Cost Variance Investigation Problem

This paper develops a warning zone approach to make variance investigation decisions for a multiperiod process. The assumed cost generation process varies between an in-control and out-of-control state. These states cannot be directly observed, but must be inferred from the reported cost variances. Using the warning zone method of inference, the manager investigates the process whenever an upper threshold is exceeded or a lower threshold is exceeded for two consecutive periods. A four-state Markov chain models the resulting decision process. Steady state probabilities are derived for this chain and are used to obtain explicit formulas for the effectiveness and efficiency of the decision process. These formulas permit computation of the cost savings attainable by the warning zone method. Compared to other decision rules, the warning zone method is much simpler than the theoretically optimal Bayesian revision method, but uses more information than the Markovian control limit method. Numerical comparison of results shows that the warning zone method usually captures most of the available cost savings, even in cases where the Markovian control limit method does not perform well.     

Cleaning Up Water? Or Building Rural Community? Community Watershed Organizations in Pennsylvania*

Abstract Recent initiatives from state and federal government agencies have helped foster the formation of community‐based watershed organizations. Although there is a great deal of enthusiasm about the potential of these organizations to enhance water quality, relatively little attention has been paid to the impacts these organizations may have on the well‐being of rural communities more generally. Assessments of effectiveness have typically focused on specific activities and accomplishments, rather than a broader range of community‐based effects. In short, we ask whether community‐based environmental management improves community as well as environment. Our research utilized a mixed‐methods design, including a statewide mail survey of all Pennsylvania watershed organizations, followed by in‐depth interviews with 28 rural watershed organizations. This sequential approach progressively explored in more detail definitions of effectiveness, including the building of rural capacity. We find watershed organizations are potentially effective mechanisms for building local leadership, enhancing the skills of rural residents, and making valuable connections with other communities, facing similar water‐resource and rural‐development issues. However, the range of issues with which local watershed organizations engage and the methods they currently utilize may eventually limit their usefulness.