Validation of sociometric structure by data on individuals' attributes

Longstanding challenges to relate sociometric structure of an intact social group to other social variables are answered first by obtaining a partition of a set of 69 inmates in Cook County Jail, using a clustering algorithm (CONCOR) applied to sociometric data. We then demonstrate that the resulting partition can be accounted for by substantively interpretable variables (e.g. number of years of school prior to incarceration) measured on the individual inmates. The linear discriminant function used to relate the two types of data does a good job of accounting for processes generating sociometric ties of friendship. It is argued that this methodology can be used to study the diversity of inmate organizational structure.     

Manipulability measures of common social choice functions

All social choice functions are manipulable when more than two alternatives are available. I evaluate the manipulability of the Borda count, plurality rule, minimax set, and uncovered set. Four measures of manipulability are defined and computed stochastically for small numbers of agents and alternatives.  Social choice rules derived from the minimax and uncovered sets are found to be relatively immune to manipulation whether a sole manipulating agent has complete knowledge or absolutely no knowledge of the preferences of the others. The Borda rule is especially manipulable if the manipulating agent has complete knowledge of the others. Received: 5 January 1996/Accepted: 31 July 1998     

Adolescent network positions and memory performance in adulthood: Evidence from sibling fixed effects models with sociometric network data

Although research has explored social factors influencing memory performance during adolescence, the impact of adolescent social network positions remains largely unknown. This study examines whether adolescent network position is associated with memory performance in adulthood, while also considering potential gender differences. The study used a sibling sample from the National Longitudinal Study of Adolescent to Adult Health (N = 2462) and employed sibling fixed effects models to account for unobserved family background factors, such as genetics, parental characteristics, family environment, and childhood neighborhood. Four dimensions of adolescent network position—i.e., popularity, sociality, degree centrality, and closeness centrality—were sociometrically assessed in schools. Memory performance in adulthood was measured using the Rey Auditory Verbal Learning Test. The sibling fixed effects estimates indicate that sociality, degree centrality, and closeness centrality are significantly associated with increased memory performance in adulthood, even after controlling for unobserved family heterogeneity as well as a set of individual-level covariates. In contrast, controlling for unobserved family heterogeneity attenuated the association for popularity, making it statistically insignificant. This study also provides evidence of gender differences in the association between social network position and memory performance. The associations for popularity, sociality, and degree centrality are more pronounced among men than women. This study’s findings highlight the importance of adolescent network positions as social determinants in shaping cognitive outcomes over the life course. Interventions that encourage positive peer interactions and reduce social isolation during adolescence may help improve cognitive health in the population.     

Estimating network properties from snowball sampled data

This article addresses the estimation of topological network parameters from data obtained with a snowball sampling design. An approximate expression for the probability of a vertex to be included in the sample is derived. Based on this sampling distribution, estimators for the mean degree, the degree correlation, and the clustering coefficient are proposed. The performance of these estimators and their sensitivity with respect to the response rate are validated through Monte Carlo simulations on several test networks. Our approach has no complex computational requirements and is straightforward to apply to real-world survey data. In a snowball sample design, each respondent is typically enquired only once. Different from the widely used estimator for Respondent-Driven Sampling (RDS), which assumes sampling with replacement, the proposed approach relies on sampling without replacement and is thus also applicable for large sample fractions. From the simulation experiments, we conclude that the estimation quality decreases with increasing variance of the network degree distribution. Yet, if the degree distribution is not to broad, our approach results in good estimates for the mean degree and the clustering coefficient, which, moreover, are almost independent from the response rate. The estimates for the degree correlation are of moderated quality.     

On the equivalence of coalitional and individual strategy-proofness properties

In this paper, we introduce a sufficient condition on the domain of admissible preferences of a social choice mechanism under which the properties of individual and coalitional strategyproofness are equivalent. Then, we illustrate the usefulness of this general result in the case where a fixed budget has to be allocated among several pure public goods. We would like to express our deepest gratitude to our referee for an extremely careful and detailed report. His/her challenging questions did force us to be more acute on the scope of validity and the limits of our result. We would like also to thank Bernardo Moreno for pointing out a mistake in the statement of Theorem 1 as it was formulated in an earlier version and for sending a copy of his joint work with Barbera et al. (2008). This is the only one paper we know of, offering an alternative systematic analysis of the question explored in our paper.     

Decomposition properties of dual choice functionals

The Gini coefficient is a well-known measure of inequality, and it satisfies a non-overlapping additive decomposition property (Ebert 1988b). The Gini coefficient is related to the dual theory of choice, as developed by Yaari (1987, 1988). We determine which other dual choice functionals satisfy a non-overlapping additive decomposition property that is weaker than the additive one suggested in Ebert (1988b). It turns out that the only functionals that do are those that arise from the Lebesgue measure, the measure associated with the Gini coefficient, and degenerate delta functions. Received: 8 January 2001/Accepted: 22 February 2002 We thank the Actuarial Education and Research Fund for financial support of this project. We also thank anonymous referees for helpful comments.     

On summary measures of binarized dominance data

Data on outcomes of dominance contests in groups of animals are often binarized (the original matrix of counts transformed into a matrix of ones and zeros indicating, for each pair, which animal won more contests). Various measures attempt to summarize the structure of the binarized data. We discuss uncertainty in such summary measures, and suggest ways to account for this uncertainty. We consider the summary measure both for an observed finite sample and for the unobserved underlying probability structure. We illustrate the general ideas with one particular summary measure, Appleby's K, and one data set, Appleby's red deer data.     

Social networks and innovation adoption: A look at burt's use of structural equivalence

This paper examines Burt's 1982 model of innovation adoption based on an application of structural equivalence. The proposition that two structurally equivalent actors will adopt an innovation at approximately the same time is explored. The diffusion of two innovations through a network of commercial fishermen provides the basis for an empirical test. Tentative support for this proposition is found, particularly if the effects of information availability, economic competition, and the appropriateness of the innovation are taken into account.     

Freedom of choice and diversity of options: Some difficulties

This paper explores the possibility for a (non-preference-based) freedom ranking of opportunity sets that is sensitive to the diversity of the options. It turns out that how distances between sets and alternatives are measured is crucial to the derivation of such a ranking. Several proposals are examined, each of which is shown to lead to impossibility results. Earlier versions of this paper were presented at conferences in Kortrijk, Osnabrück, Oisterwijk, Caen and Pavia. I thank the participants at these conferences for their comments. I would also like to thank Steven Hartkamp, Theo Kuipers, Clemens Puppe and especially Kotaro Suzumura for their helpful comments. Furthermore, I am very grateful to Somdeb Lahiri for pointing out a mistake in a previous version of this paper.     

Subjective measures of risk aversion, fixed costs, and portfolio choice

The paper investigates risk preferences among different types of individuals. We use several different measures of risk preferences, including questions on choices between uncertain income streams suggested by Barsky, Juster, Kimball, and Shapiro (1997) and a number of ad hoc measures. As in [Barsky et al., 1997] and [Arrondel and Calvo-Pardo, 2002], we first analyze individual variation in the risk aversion measures and explain them by background characteristics (both “objective” characteristics and other subjective measures of risk preference). Next we incorporate the measured risk preferences into a household portfolio allocation model, which explains portfolio shares, while accounting for incomplete portfolios and fixed costs. Our results show that a measure based on factor analysis of answers to a number of simple risk preference questions has the most explanatory power. The Barsky et al. (1997) measure has less explanatory power than this “a-theoretical” measure, suggesting that sophisticated measures based on economic theory may exceed the financial capability of respondents. Fixed costs turn out to provide an economically and statistically highly significant explanation for incomplete portfolios.     

Comparison of seven measures of sickness absence based on data from three counties in Sweden

The objective was to compare the applicability of and results provided by the two measures of sickness absence used most often within the Swedish social insurance administration (that is, unadjusted sick-leave rate and adjusted sick-leave rate) and five measures suggested by epidemiological researchers. Data consisted of four cross-sectional data sets of registry sick-leave data covering four separate years (1997-2000) in three counties. In total 454,000 persons qualified for sickness insurance and aged 20-64 years were included. The two measures used within the social insurance administration and three of the five measures suggested by epidemiological researchers revealed sex-related dissimilarities in absence patterns that indicated that women had more sickness absence than men. However, in marked contrast to those results, two of the epidemiologically based measures (i.e., length of sickness absence and duration of sickness absence) instead showed highly comparable rates of sick leave for men and women, and such information is seldom obtained, albeit definitely of importance, when trying to make a correct assessment of sickness absence. The measure of sickness absence that is used influences the findings and should therefore be chosen with care. Complementing the measures used in the social insurance administration by five measures suggested by epidemiological researchers provided a more informative and comprehensive picture of sickness absence in a population. Further investigations into the effect of using different measures is needed, as well as international consensus on what to call different measures.     

Some unique properties of eigenvector centrality

Eigenvectors, and the related centrality measure Bonacich's c(β), have advantages over graph-theoretic measures like degree, betweenness, and closeness centrality: they can be used in signed and valued graphs and the beta parameter in c(β) permits the calculation of power measures for a wider variety of types of exchange. Degree, betweenness, and closeness centralities are defined only for classically simple graphs—those with strictly binary relations between vertices. Looking only at these classical graphs, where eigenvectors and graph–theoretic measures are competitors, eigenvector centrality is designed to be distinctively different from mere degree centrality when there are some high degree positions connected to many low degree others or some low degree positions are connected to a few high degree others. Therefore, it will not be distinctively different from degree when positions are all equal in degree (regular graphs) or in core-periphery structures in which high degree positions tend to be connected to each other.     

Impact of methods for reducing respondent burden on personal network structural measures

We examine methods for reducing respondent burden in evaluating alter–alter ties on a set of network structural measures. The data consist of two sets, each containing 45 alters from respondent free lists: the first contains 447 personal networks, and the second 554. Respondents evaluated the communication between 990 alter pairs. The methods were (1) dropping alters from the end of the free-list, (2) randomly dropping alters, (3) randomly dropping links, and (4) predicting ties based on transitivity. For some measures network structure is captured with samples of less than 20 alters; other measures are less consistent. Researchers should be aware of the need to sample a minimum number of alters to capture structural variation.     

On the robustness of centrality measures under conditions of imperfect data

An analysis is conducted on the robustness of measures of centrality in the face of random error in the network data. We use random networks of varying sizes and densities and subject them (separately) to four kinds of random error in varying amounts. The types of error are edge deletion, node deletion, edge addition, and node addition. The results show that the accuracy of centrality measures declines smoothly and predictably with the amount of error. This suggests that, for random networks and random error, we shall be able to construct confidence intervals around centrality scores. In addition, centrality measures were highly similar in their response to error. Dense networks were the most robust in the face of all kinds of error except edge deletion. For edge deletion, sparse networks were more accurately measured.     

Does structure find structure?: A critique of Burt's use of distance as a measure of structural equivalence

This paper examines some of the assumptions and consequences of the use of distance as a measure of structural equivalence, as implemented in Burt's STRUCTURE program. We take the general perspective that for a measure to be useful it should not confound separate types of information which are theoretically and mathematically independent. The mathematical relationship between distance and the Pearson product moment correlation coefficient is presented. We show that use of distance as a measure of similarity without proper attention to appropriate standardization procedures confounds information on differences between means and differences between variances with information on the similarity of the patterns between pairs of individuals, e.g. correlation. A detailed examination of Burt and Bittner's analysis of Bernard, Killworth and Sailer's Ham radio operator group is presented, and it is demonstrated that use of distance as a measure of structural equivalence led to nonsensical results.     

Farm size shapes friend choice amongst rice producers in China: Some evidence for the theory of network ecology

Multiple dynamics jointly determine who we befriend, however, researchers have failed to systematically assess which processes matter most under different circumstances. Here I draw on observations around how the demands of paddy rice cultivation shape social interaction to demonstrate that the relative importance of reciprocity, transitivity and generalised exchange to who rice producers choose as friends varies with the amount of agricultural land under their control. In doing so, I use unique data on farm size and friendship amongst 4713 rice-growing smallholders in 162 rural villages in Jiangxi, China along with a new technique for measuring the relative importance of effects in Stochastic Actor-Oriented Models. In line with the micro-level component of the recently advanced “theory of network ecology”, results suggest that features of an individual’s proximal environment can powerfully moderate the relative expression of network-formation mechanisms such that for some individuals, a dynamic may be expected to hold substantial sway over the process of choosing social contacts and, for others, no sway at all.     

入世后甘肃乡镇企业发展的困难与措施

随着西部大开发步伐的加快，甘肃乡镇企业也得到了较快的发展，近几年已经成为甘肃省工业经济中的一支有生力量。目前甘肃国内生产总值的18．5％、工业增加值的24．4％都是由乡镇企业创造的，乡镇企业实缴税金占全省大口径财政收入的12％。到2001年底，甘肃乡镇企业个数已达到23．6万个，