Birth outcome, not pregnancy process: Reply to van der Veen

In a recent article (Frisbie. Forbes. and Pullum 1996) we documented racial/ethnic differences in birth outcomes according to a more fine-grained classification than has typically been employed in the demographic literature. In his commentary, van der Veen focuses on the measurement of one of the dimensions of that classification, maturity of the infant. as proxied by the fetal growth ratio. The crux of the critique is easily seen in van der Veen's statement that “all of my disagreements with Frisbie et al. 's method arise from their particular use of a postnatal standard for the assessment of intrauterine growth.” Our critic misunderstands our objective: He fails to realize our interest in birth outcome, not pregnancy process, and does not perceive that our intent was to extend the research extant in both the demographic and public-health literatures in which patently postnatal (i.e., ex utero) measures are taken as outcomes interesting in their own right and/or as risk factors for infant mortality and infant and childhood morbidity. Specifically, he does recognize that we purposefully expanded our focus to include moderately compromised births to determine if they were at higher risk than the normal births with whom they are conventionally categorized. Our discussion draws on research cited in the original article, on studies cited by our critic, and on a few more recent investigations. Although we have never argued that ours is the only, or even the best, approach in all cases, we try to clarify the rationale for, and adduce additional empirical evidence of, the utility of the method we used.     

Beyond single mothers: Cohabitation and marriage in the AFDC program

We investigate the extent and implications of cohabitation and marriage among U.S. welfare recipients. An analysis of four data sets (the Current Population Survey, the National Survey of Families and Households, the Panel Study of Income Dynamics, and the National Longitudinal Survey of Youth) shows significant numbers of cohabitors among recipients of AFDC. An even more surprising finding is the large number of married women on welfare. We also report the results of a telephone survey of state AFDC agencies conducted to determine state rules governing cohabitation and marriage. The survey results indicate that, in a number of respects, AFDC rules encourage cohabitation. Finally, we conduct an analysis of the impact of AFDC rules on cohabitation, marriage, and single motherhood and find weak evidence in support of incentives to cohabit.     

TEACHING EFFECTIVENESS IN THE DECISION SCIENCES: THE USE OF STUDENT EVALUATIONS

This article presents the results of an AIDS-sponsored investigation of teaching effectiveness in the decision sciences. Two national samples were employed in the study: a sample of 247 business school deans and a sample of 3,292 students from 32 different business schools. Included among the findings are that 87 percent of the deans responding indicate they require some sort of faculty teaching effectiveness evaluation, and that great care must be exercised when interpreting student ratings of an individual instructor's teaching effectiveness.     

MULTIPLE REGRESSION ANALYSIS APPLIED TO RESIDENTIAL PROPERTIES

An interesting and promising innovation in the assessment of property for tax purposes is the application of multiple regression analysis. Sales prices are regressed on various housing characteristics, and models developed from sold properties are used to generate value estimates for unsold properties. Two important issues relating to the development of such models are (1) the extent to which real estate markets are stable in terms of structural relationships over time, and (2) the extent to which sales prices reflect actual market values. The first issue is important because it affects how current sales must be before they can be used in model development, as well as the amount of information the assessor must collect and maintain on properties. The second issue is important because it concerns the amount of measurement error in the models and the extent to which the assessor/analyst can unambiguously interpret residual variance. These issues are investigated by comparing regression models developed from a sample of properties in Eugene, Oregon, which sold in each of two well separated time periods.     

SENSITIVITY ANALYSIS WITH INTERACTION EFFECTS

The purpose of this paper is to extend the sensitivity analysis methodology as it applies to linear programming. The methodology developed herein is concerned with those changes in a technological coefficient that cause simultaneous changes in the relevant cost coefficients of the objective function. By proceeding from the definitions of feasibility and optimality, the authors develop formulas for determining bounds on the extent to which a technological coefficient, which has a predetermined effect on the corresponding cost coefficient, can vary without changing the optimal set of activities. After the formulas are developed, their use is demonstrated on a product-mix problem. This technique is of interest because changes in the rate at which an input is utilized can be expected to change the cost per unit of a resulting product. This interdependence should be recognized whenever a sensitivity analysis is performed on a technological coefficient of either a cost minimization or a contribution margin maximization problem.     

ANALYZING GEOGRAPHICALLY DISCRETE WAREHOUSING NETWORKS BY COMPUTER SIMULATION*

This paper describes a comprehensive simulation modeling approach to the problem of locating warehousing facilities in a fashion that minimizes the cost associated with operating a multi-product, multi-source, multi-destination distribution system. The digital simulation model presented in the study is derived within an “industrial dynamics” framework, utilizes input from an existing management information system, and employs a number of relatively simple heuristic procedures to analyze various alternative warehousing networks. Simulation results, in terms of the distribution costs associated with various warehouse locations, are presented for cases involving the effect of provision of a 100% service level, the effect of constraining product availability and/or inventory capacities at various warehouses, and the effect of deleting various warehouses from the existing warehouse network.