Inverse Combinatorial Optimization: A Survey on Problems, Methods, and Results

Given a (combinatorial) optimization problem and a feasible solution to it, the corresponding inverse optimization problem is to find a minimal adjustment of the cost function such that the given solution becomes optimum.Several such problems have been studied in the last twelve years. After formalizing the notion of an inverse problem and its variants, we present various methods for solving them. Then we discuss the problems considered in the literature and the results that have been obtained. Finally, we formulate some open problems.     

Die Rettung von Juden im Zweiten Weltkrieg

The rescue of Jews in WWII was in many respects extraordinary. For theories of action in the social sciences, these acts pose the challenge to explain pro-social behavior in the face of great risks. Whereas the overwhelming bulk of the literature points towards a specific altruistic personality or identity, rational choice explanations emphasize the significance of incentives and opportunities to help. Based on the Model of Frame Selection, the article develops an integrative explanation that allows resolution of this debate and that identifies constellations of causal factors conducive to helping. To empirically test this explanation, the empirical analyses use data that were collected retrospectively in the 1980s by the Altruistic Personality and Prosocial Behavior Institute (Oliner and Oliner 1988, The altruistic personality: Rescuers of Jews in Nazi Europe, 1988). Statistically, I employ Boolean probit models, a statistical method hardly known in sociology which allows reconstruction of complex patterns of causal interaction. The analyses corroborate the developed explanation. Acts of help could result either spontaneously, in reaction to being asked for help and based on strong pro-social orientations, or deliberatingly, depending on the constellation of incentives and opportunities.     

Impacts of the Triple Global Crisis on Growth and Poverty: The Case of Yemen

Yemen is an oil‐exporting and food‐importing country with the highest levels of poverty in the Middle East and North Africa. The impacts of the triple crisis are likely to further complicate pre‐existing conditions of conflict, oil depletion and governance failure. Using a dynamic CGE model, this article finds that oil‐driven growth in 2008 dominated the negative growth impacts of the food crisis, but that growth was not pro‐poor. The financial crisis of 2009 slowed growth sharply and raised the poverty rate to 42.8%, up from 34.8% in 2005/6. Poverty continues to be higher in rural areas, where almost half the population live in poverty.     

Either with us or against us: experimental evidence on partial cartels

This paper analyzes the coordination challenge a partial cartel faces when payoff asymmetries between potential cartel insiders and potential cartel outsiders are large. We introduce two experimental treatments: a standard treatment where a complete cartel can be supported in a Nash equilibrium and a modified treatment where a complete cartel and a partial cartel can both be supported in a Nash equilibrium. To assess the role of communication both treatments are additionally run with a “chat option,” yielding four treatments in total. Our results show that subjects frequently reject the formation of partial cartels in the modified treatments. In all treatments with communication subjects are more likely to form complete cartels than partial cartels. The implications of these results are important for antitrust: payoff asymmetries between cartel members and outsiders may jeopardize the formation of partial cartels. Yet complete cartels may be formed instead, if institutional mechanisms with frequent communication are used to form cartels.

     

A future agenda for research on climate change and human mobility

In the past 15 years, research activities focusing on the interlinkages between climate change and human mobility have intensified. At the same time, an increasing number of actors and processes have sought to address human mobility in the context of climate change from a policy perspective. Hitherto, research has been limited in terms of geographical preferences as well as conceptual and methodological focus areas. This paper argues that to address the evolving policy space, future research on climate change in the context of human mobility needs to become more differentiated, integrated and generalized. This includes concerted efforts to better integrate researchers from the global South, improved cross-linkages between different datasets, approaches and disciplines, more longitudinal and comparative studies and development of innovative qualitative and quantitative methods.