@article{MetternichWucherpfennig, author = {Metternich, Nils W. and Wucherpfennig, Julian}, title = {Strategic rebels: a spatial econometric approach to rebel fighting durations in civil wars}, series = {International Interactions}, volume = {46}, journal = {International Interactions}, number = {2020}, doi = {10.1080/03050629.2020.1737800}, abstract = {Recent research on multi-actor civil wars highlights that rebel organizations condition their conflict behavior on that of other rebel organizations, with competition and free-riding constituting the core theoretical mechanisms. We provide a new actor-centric approach to explicitly model strategic interdependence in multi-actor civil wars. We argue that rebel organizations have incentives to remain mobilized until the end of a conflict to maintain their power to negotiate, power to spoil, power to enforce, and power to protect. This induces strategic complements that dominate duration dynamics in multi-actor conflicts. Based on a network game-theoretic model, we derive a spatial econometric framework that allows for a direct test of strategic interdependence. We find that the estimated duration interdependence is positive but partially offset in secessionist conflicts where the public goods nature of the incompatibility also induces strategic substitution effects.}, language = {en} } @article{PoloWucherpfennig2021, author = {Polo, Sara M.T. and Wucherpfennig, Julian}, title = {Trojan Horse, Copycat, or Scapegoat? Unpacking the Refugees-Terrorism Nexus}, series = {The Journal of Politics}, volume = {84}, journal = {The Journal of Politics}, number = {1}, doi = {10.1086/714926}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:b1570-opus4-38244}, pages = {33 -- 49}, year = {2021}, abstract = {Widespread fear that hosting refugees will mean more terrorism in host states is at the heart of the 'refugee crisis'. Yet, we lack rigorous evidence for such claims. This article theoretically unpacks how and under what conditions transnational refugee movements plausibly lead to different types of terrorist outcomes. Combining original data with a multi-pronged approach involving a treatment-placebo design as well as instrumental variable estimation, we provide systematic and robust evidence that sheds new light on the security implications of forced migration. Our findings challenge the claim that hosting refugees heightens the risk of "importing" terrorist attacks against nationals of host countries, especially in developed countries. However, in these countries refugees themselves are particularly prone to becoming the targets of terrorist attacks by natives, driven by fear and revenge. Dominant policy responses to the refugee crisis that raise fears and suspicions are therefore not only ill-suited, but potentially counterproductive.}, language = {en} } @article{WucherpfennigKachiBormannetal., author = {Wucherpfennig, Julian and Kachi, Aya and Bormann, Nils-Christian and Hunziker, Philipp}, title = {A Fast Estimator for Binary Choice Models with Spatial, Temporal, and Spatio-Temporal Interdependence}, series = {Political Analysis}, volume = {29(4)}, journal = {Political Analysis}, doi = {10.1017/pan.2020.54}, pages = {570 -- 576}, abstract = {Binary outcome models are frequently used in the social sciences and economics. However, such models are difficult to estimate with interdependent data structures, including spatial, temporal, and spatio-temporal autocorrelation because jointly determined error terms in the reduced-form specification are generally analytically intractable. To deal with this problem, simulation-based approaches have been proposed. However, these approaches (i) are computationally intensive and impractical for sizable datasets commonly used in contemporary research, and (ii) rarely address temporal interdependence. As a way forward, we demonstrate how to reduce the computational burden significantly by (i) introducing analytically-tractable pseudo maximum likelihood estimators for latent binary choice models that exhibit interdependence across space and time and by (ii) proposing an implementation strategy that increases computational efficiency considerably. Monte Carlo experiments show that our estimators recover the parameter values as good as commonly used estimation alternatives and require only a fraction of the computational cost.}, language = {en} } @techreport{SorgWucherpfennig, type = {Working Paper}, author = {Sorg, Alexander and Wucherpfennig, Julian}, title = {Before deploying more U.S. forces to Europe, consider the consequences}, series = {War on the Rocks}, journal = {War on the Rocks}, language = {en} } @article{RodriguezSanchezWucherpfennigRischkeetal., author = {Rodr{\´i}guez S{\´a}nchez, Alejandra and Wucherpfennig, Julian and Rischke, Ramona and Iacus, Stefano Maria}, title = {Search-and-rescue in the Central Mediterranean Route does not induce migration: Predictive modeling to answer causal queries in migration research}, series = {Scientific Reports}, volume = {13}, journal = {Scientific Reports}, number = {1}, doi = {10.1038/s41598-023-38119-4}, abstract = {State- and private-led search-and-rescue are hypothesized to foster irregular migration (and thereby migrant fatalities) by altering the decision calculus associated with the journey. We here investigate this 'pull factor' claim by focusing on the Central Mediterranean route, the most frequented and deadly irregular migration route towards Europe during the past decade. Based on three intervention periods—(1) state-led Mare Nostrum, (2) private-led search-and-rescue, and (3) coordinated pushbacks by the Libyan Coast Guard—which correspond to substantial changes in laws, policies, and practices of search-and-rescue in the Mediterranean, we are able to test the 'pull factor' claim by employing an innovative machine learning method in combination with causal inference. We employ a Bayesian structural time-series model to estimate the effects of these three intervention periods on the migration flow as measured by crossing attempts (i.e., time-series aggregate counts of arrivals, pushbacks, and deaths), adjusting for various known drivers of irregular migration. We combine multiple sources of traditional and non-traditional data to build a synthetic, predicted counterfactual flow. Results show that our predictive modeling approach accurately captures the behavior of the target time-series during the various pre-intervention periods of interest. A comparison of the observed and predicted counterfactual time-series in the post-intervention periods suggest that pushback policies did affect the migration flow, but that the search-and-rescue periods did not yield a discernible difference between the observed and the predicted counterfactual number of crossing attempts. Hence we do not find support for search-and-rescue as a driver of irregular migration. In general, this modeling approach lends itself to forecasting migration flows with the goal of answering causal queries in migration research.}, language = {en} } @article{SorgWucherpfennig, author = {Sorg, Alexander and Wucherpfennig, Julian}, title = {Do Foreign Military Deployments Provide Assurance? Unpacking the Micro-Mechanisms of Burden Sharing in Alliances}, series = {International Studies Quarterly}, volume = {68}, journal = {International Studies Quarterly}, number = {3}, publisher = {Oxford University Press}, issn = {0020-8833}, doi = {10.1093/isq/sqae107}, abstract = {How do US foreign military deployments impact the defense policies of host states? Dominant scholarship holds that these deployments play a pivotal role in assuring allies that their security is guaranteed, which in turn leads host countries to neglect their national defense contributions. In this research note, we examine the micro-foundations of this conventional wisdom, investigating how nuclear and conventional troop deployments impact attitudes toward defense policies in (potential) host states. We highlight that the presumed linkage between assurance and free-riding critically implies that foreign military deployments must positively affect perceptions of security among host nations. We test this core logic, alongside some alternative pathways, at the micro level through two survey experiments that randomize hypothetical withdrawals (Germany) and deployments (Czech Republic). Although we find some evidence that foreign military deployments can decrease citizens' subjective need for defense, the survey experiments also reveal that citizens hardly feel protected by these deployments. Thus, our results cast doubt on the core logic underlying the theory of free-riding in alliances.}, language = {en} }