Practical Collapsed Stochastic Variational Inference for the HDP

Recent advances have made it feasible to apply the stochastic variational paradigm to a collapsed representation of latent Dirichlet allocation (LDA). While the stochastic variational paradigm has successfully been applied to an uncollapsed representation of the hierarchical Dirichlet process (HDP), no attempts to apply this type of inference in a collapsed setting of non-parametric topic modeling have been put forward so far. In this paper we explore such a collapsed stochastic variational Bayes inference for the HDP. The proposed online algorithm is easy to implement and accounts for the inference of hyper-parameters. First experiments show a promising improvement in predictive performance.Comment: NIPS Workshop; Topic Models: Computation, Application, and Evaluatio

Horizontal Inequalities and Violent Conflict. Côte d’Ivoire Country Paper

human development, aid, trade, security

Between fallacy and feasibility? Dealing with the risk of ecological fallacies in the quantitative study of protest mobilization and conflict

In recent years, the quantitative study of conflict has increasingly focused on small-scale and/or localized conflicts in the developing world. In this paper, we analyze and critically reflect upon a major methodological shortcoming of many studies in this field of research. We argue that by using group- or macro-level empirical data and modelling techniques, while at the same time theoretically underpinning observed empirical associations with individual-level mechanisms, many of these studies risk committing an ecological fallacy. The individual-level mechanism on which many studies rely concerns the presence of grievances which mobilize people to participate in contentious politics. This motivational approach was also present in early studies on protest mobilization in Western societies, which often relied on similar research designs. However, subsequent advances in this literature and the use of methods that were targeted more directly at the individual level uncovered that grievances alone cannot explain mobilization and that organizational capabilities and complex psychological mechanisms of belonging also form part of the puzzle. While drawing on conflict events as well as survey data from Africa, we demonstrate empirically that here, as well, inferring micro-level relations and dynamics from macro-level empirical models can lead to erroneous interpretations and inferences. Hence, we argue that to improve our understanding of conflict mobilization in the developing world, especially for conflicts with low levels of violence, it is necessary to substantially expand our methodological toolbox beyond macro-level analyses

The Implications of Horizontal Inequality for Aid

This paper argues that the reduction of horizontal inequalities (HIs) or inequalities between culturally defined groups should inform aid policy in heterogeneous countries with severe HIs. It shows how this would change aid allocation across countries, leading to more aid to heterogeneous countries relative to homogeneous ones, the opposite of the existing bias in aid distribution. It explores how adopting an HI approach would affect the use of particular aid instruments, arguing that different instruments are appropriate according to the attitude and capacity of the government in relation to correcting HIs. Drawing on case studies of Ghana and Nepal it argues that at present there is neglect of HI considerations in aid policy, which can be particularly damaging where aid forms a large part of government resources.aid, horizontal inequality, social exclusion, Nepal, Ghana