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ROW by Dr. Çağıl Koçyiğit
Time: Sep 18, 2026 at 15:00 CET
Title: Learning Risk Scores Robust to Unobserved Confounders
Abstract: We consider the problem of learning risk scores to prioritize individuals for scarce resources or interventions, from historical observational data affected by unobserved confounding. In settings such as public health and homelessness prevention, decisions about who receives a scarce resource (e.g., a hospital bed or housing) are often guided by a risk score assigned to each individual based on recorded characteristics, such as responses to a survey. These risk scores are increasingly being learned directly from observational data: historical records of individuals' characteristics, allocation decisions, and outcomes under received allocations. Standard methods such as inverse propensity weighting (IPW), which corrects for the bias introduced by the historical allocation policy, can be used to learn accurate risk scores if the historical decision process is fully explained by the recorded characteristics, an assumption known as unconfoundedness. In practice, however, historical decisions often depend on unrecorded information (e.g., details a caseworker learns in conversation but never logs), causing learned risk scores to systematically under-prioritize exactly the individuals whose unrecorded circumstances drove past prioritization. We propose a method for learning risk scores that are robust to this kind of unobserved confounding, building on IPW. Since propensity weights cannot be reliably estimated under unobserved confounding, we instead treat them as belonging to an uncertainty set determined by the observable data and domain-informed estimates of the degree of confounding, combining sensitivity analysis from causal inference with Wasserstein distributionally robust optimization. The resulting robust risk score learning problem admits a sample-based approximation that we reformulate as an exponential conic program compatible with off-the-shelf solvers. We demonstrate the effectiveness of our approach relative to IPW and other benchmarks on semi-synthetic data derived from datasets in the UCI Machine Learning Repository. Beyond risk scores, this way of representing unobserved confounding as an uncertainty set is not specific to our setting and can be used to robustly learn other causal quantities of interest.
Short bio: Çağıl Koçyiğit is an associate professor at the Department of Engineering and the Department of Economics and Management, University of Luxembourg. Her research focuses on optimization under uncertainty with applications in policy and mechanism design. Her work has been published in prestigious journals including Management Science, Operations Research, and Mathematical Programming, and she has received multiple awards and recognition for her work. She holds a Ph.D. in Management of Technology from École Polytechnique Fédérale de Lausanne (EPFL).
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