Working toward effective anonymization for surveillance data: innovation at South Africa’s Agincourt Health and Socio-Demographic Surveillance Site

Linking people and places is essential for population-health-environment research. Yet, this data integration requires geographic coding such that information reflecting individuals or households can appropriately be connected with characteristics of their proximate environments. However, offering access to such geocoding greatly increases the risk of respondent identification and, therefore, holds the potential to breach confidentiality. In response, a variety of “geographic masking” techniques have been developed to introduce error into geographic coding and thereby reduce the likelihood of identification. We report findings from analyses of the error introduced by several masking techniques applied to data from the Agincourt Health and Socio-Demographic Surveillance System in rural South Africa. Using a vegetation index (Normalized Difference Vegetation Index (NDVI)) at the household scale, comparisons are made between the “true” NDVI values and those calculated after masking. We also examine the tradeoffs between accuracy and protecting respondent privacy. The exploration suggests that in this study setting and for NDVI, geomasking approaches that use buffers and account for population density produce the most accurate results. However, the exploration also clearly demonstrates the tradeoff between accuracy and privacy, with more accuracy resulting in a higher level of potential respondent identification. It is important to note that these analyses illustrate a process that should characterize spatially informed research but within which particular decisions must be shaped by the research setting and objectives. In the long run, we aim to provide insight into masking’s potential and perils to facilitate population-environment-health research.

     

Conflicts over farming practices in Canada: the role of interactive conflict resolution approaches

An increasing number of articles in professional and scientific journals, as well as in the public press, give evidence to a rising number of conflicts that exist in rural communities. These conflicts arise from changes in farming practices, the increasing number of large-scale production units, resource use, and demographics. Fair, effective and efficient approaches to resolve these conflicts are of increasing interest and importance. An interactive conflict resolution (ICR) approach that focuses on communication and positive social interactions may be a preferred approach for resolving conflicts. The role of ICR approaches in addressing conflicts arising from farming and agri-business practices is presented and discussed in this paper. The paper posits that ICR approaches are efficient from an economic as well as a social perspective and that they provide the greatest potential to realize socially optimal outcomes from a both a theoretical and practical perspective.     

Estimation of the sum of differences distribution

Consider the distribution of Z_i d_iwhere the d.d_i?s are 1=1 lldifferences independently, identically and symmetrically distributed with mean zero. The problem is to determine properties of the sdd given the distribution of the d._i?fs and the sample size n. The standardized moments as a function of the moments of the d._i!s are developed. A variance reduction technique for estimating the quantiles of the sdd using Monte Carlo methods is developed based on using the randomization sample consisting of the 2ⁿ values of Z _i+d. rather than the single observation i=l lZ d. corresponding to each sample d_id_n. The randomization sample is shown to produce unbiased and consistent estimators.     

Natural family planning: A comparison of continuers and discontinuers

Little research has been done on social-psychological variables related to the use of natural family planning. The objective of this study was to analyze variables that differentiated between continuers and discontinuers of natural family planning (NFP). Questionnaires were obtained from couples who had received instruction in the sympto-thermal method of natural family planning at a large urban hospital. Subjects who were attempting to become pregnant or who were using other methods of contraception in conjunction with NFP were deleted from the analysis, leaving N of 74. With Pearson correlation, variables significantly related (p<.05) to NFP continuance were: religiosity, planning more children, perceived severity of pregnancy, support from spouse and relatives, dissatisfaction with other contraceptive methods, attitudes toward NFP, perceived effectiveness of NFP, attitudes toward abstinence, and importance of intercourse.     

Phased local search for the maximum clique problem

This paper introduces Phased Local Search (PLS), a new stochastic reactive dynamic local search algorithm for the maximum clique problem. (PLS) interleaves sub-algorithms which alternate between sequences of iterative improvement, during which suitable vertices are added to the current clique, and plateau search, where vertices of the current clique are swapped with vertices not contained in the current clique. The sub-algorithms differ in their vertex selection techniques in that selection can be solely based on randomly selecting a vertex, randomly selecting within highest vertex degree or randomly selecting within vertex penalties that are dynamically adjusted during the search. In addition, the perturbation mechanism used to overcome search stagnation differs between the sub-algorithms. (PLS) has no problem instance dependent parameters and achieves state-of-the-art performance for the maximum clique problem over a large range of the commonly used DIMACS benchmark instances.     

Changes in Management Ownership and the Valuation Effects of Equity Offerings

Seasoned equity issues trigger share price declines, and this is usually interpreted as evidence of signalling. We find that seasoned equity issues also typically result in much lower managerial ownership in U.S. firms. Jensen and Meckling (1976) predict a stock price decline when managerial ownership falls. We conduct several tests to distinguish agency explanations form signalling explanations, and conclude that both effects are present.     

An Exponential-Family Multidimensional Scaling Mixture Methodology

A multidimensional scaling methodology (STUNMIX) for the analysis of subjects' preference/choice of stimuli that sets out to integrate the previous work in this area into a single framework, as well as to provide a variety of new options and models, is presented. Locations of the stimuli and the ideal points of derived segments of subjects on latent dimensions are estimated simultaneously. The methodology is formulated in the framework of the exponential family of distributions, whereby a wide range of different data types can be analyzed. Possible reparameterizations of stimulus coordinates by stimulus characteristics, as well as of probabilities of segment membership by subject background variables, are permitted. The models are estimated in a maximum likelihood framework. The performance of the models is demonstrated on synthetic data, and robustness is investigated. An empirical application is provided, concerning intentions to buy portable telephones.     

Neighbors in Time: Development and Use of Some Values for Intergenerational Justice from the Jewish and Christian Religious Traditions

The overlapping understandings of Jewish and Christian traditions (the Traditions), both influencing and reincorporating Western culture from the Greeks to the present, underpin many of the ethical constructs of present society, in ways both obvious and subtle. The concept of justice is central to the ethical outlooks of both religious traditions. This article systematically develops values related to justice from within the Traditions and extends them to the question of intergenerational equity as proposed precepts for assessment and action. Many of the results seem familiar because they are deeply embedded in our culture. They are assertions that transcend time-the value of human life; an obligation to support the necessary interests of others, especially the powerless; the concepts of brotherhood, the common good, and stewardship of resources; and the transmission of knowledge, resources, and values through the vehicles of families and communities. Other ideas from within the Traditions, such as giving beyond the requirements of equity and the connection of human life with God whose abilities are unbounded by time, continue to draw people beyond the limits of culture. These outlooks are organized into 17 statements or proposals constitutive of this view of justice. These summary statements are used as the basis for comparing a system of principles proposed by a panel of the National Academy of Public Administration for intergenerational decision making with the views represented by the Traditions. This broaches a broader question of fairness in resource distribution. The article concludes with reference to some developed resources of the Traditions from which further insight can be drawn, and another illustration related to resource allocation. It is hoped that the article helps stimulate wider analysis of the values on which our decisions are made.