Modeling homophily and stochastic equivalence in symmetric relational data

This article discusses a latent variable model for inference and prediction of symmetric relational data. The model, based on the idea of the eigenvalue decomposition, represents the relationship between two nodes as the weighted inner-product of node-specific vectors of latent characteristics. This ``eigenmodel'' generalizes other popular latent variable models, such as latent class and distance models: It is shown mathematically that any latent class or distance model has a representation as an eigenmodel, but not vice-versa. The practical implications of this are examined in the context of three real datasets, for which the eigenmodel has as good or better out-of-sample predictive performance than the other two models.Comment: 12 pages, 4 figures, 1 tabl

Mixed membership stochastic blockmodels

Observations consisting of measurements on relationships for pairs of objects arise in many settings, such as protein interaction and gene regulatory networks, collections of author-recipient email, and social networks. Analyzing such data with probabilisic models can be delicate because the simple exchangeability assumptions underlying many boilerplate models no longer hold. In this paper, we describe a latent variable model of such data called the mixed membership stochastic blockmodel. This model extends blockmodels for relational data to ones which capture mixed membership latent relational structure, thus providing an object-specific low-dimensional representation. We develop a general variational inference algorithm for fast approximate posterior inference. We explore applications to social and protein interaction networks.Comment: 46 pages, 14 figures, 3 table

The value of relationships : evidence from a supply shock to Kenyan rose exports

This paper provides evidence on the importance of reputation, intended as beliefs buyers hold about seller's reliability, in the context of the Kenyan rose export sector. A model of reputation and relational contracting is developed and tested. We show that 1) the value of the relationship increases with the age of the relationship; 2) during an exogenous negative supply shock sellers prioritize relationships consistently with the predictions of the model; and 3) reliability at the time of the shock positively correlates with future survival and relationship value. Models exclusively focussing on enforcement or insurance considerations cannot account for the evidence

MICSIM : Concept, Developments and Applications of a PC-Microsimulation Model for Research and Teaching

It is the growing societal interest about the individual and its behaviour in our and 'modern' societies which is asking for microanalyses about the individual situation. In order to allow these microanalyses on a quantitative and empirically based level microsimulation models were developed and increasingly used for economic and social policy impact analyses. Though microsimulation is known and applied (mainly by experts), an easy to use and powerful PC microsimulation model is hard to find. The overall aim of this study and of MICSIM - A PC Microsimulation Model is to describe and offer such a user-friendly and powerful general microsimulation model for (almost) any PC, to support the impact microanalyses both in applied research and teaching. Above all, MICSIM is a general microdata handler for a wide range of typical microanalysis requirements. This paper presents the concept, developments and applications of MICSIM. After some brief remarks on microsimulation characteristics in general, the concept and substantive domains of MICSIM: the simulation, the adjustment and aging, and the evaluation of microdata, are described by its mode of operation in principle. The realisations and developments of MICSIM then are portrayed by the different versions of the computer program. Some MICSIM applications and experiences in research and teaching are following with concluding remarks.Economic and Social Policy Analyses, Microsimulation (dynamic and static), Simulation, Adjustment and Evaluation of Microdata, PC Computer Program for Microanalyses in General

Volunteer work and domain satisfactions: Evidence from Italy

The paper empirically investigates if individuals who supply volunteer work are more satisfied with three domain satisfactions - leisure, friends' relationships and economic situation – than nonvolunteers. Using Istat's (Italian Central Statistical Office) Multiscopo data set for the period 1993- 2000, it finds that volunteer labour supplied in official volunteer service association is positively correlated with leisure satisfaction, friends' relationships satisfaction and economic situation satisfaction. These findings are interpreted as an indication that the benefits from volunteering are a combination of the following reasons: i) intrinsic motivation; ii) extrinsic motivation; iii) relational goods.volunteering, intrinsic and extrinsic motivations, relational goods, domain satisfactions, Multiscopo.

Microsimulation - A Survey of Methods and Applications for Analyzing Economic and Social Policy

This essential dimensions of microsimulation as an instrument to analyze and forecast the individual impacts of alternative economic and social policy measures are surveyed in this study. The basic principles of microsimulation, which is a tool for practical policy advising as well as for research and teaching, are pointed out and the static and dynamic (cross-section and life-cycle) approaches are compared to one another. Present and past developments of microsimulation models and their areas of application are reviewed, focusing on the US, Europe and Australia. Based on general requirements and components of microsimulation models a microsimulation model's actual working mechanism are discussed by a concrete example: the concept and realization of MICSIM, a PC microsimulation model based on a relational database system, an offspring of the Sfb 3 Statitic Microsimulation Model. Common issues of microsimulation modeling are regarded: micro/macro link, behavioural response and the important question of evaluating microsimulation results. The concluding remarks accentuate the increasing use of microcomputers for microsimulation models also for teaching purposes.Microsimulation, Microanalytic Simulation Models, Microanalysis, Economic and Social Policy Analysis