LLM-Powered Preference Elicitation in Combinatorial Assignment
Ermis Soumalias, Yanchen Jiang, Kehang Zhu, Michael Curry, Sven, Seuken, David C. Parkes

TL;DR
This paper explores using large language models as efficient proxies for humans in preference elicitation for combinatorial assignment, reducing effort and improving efficiency.
Contribution
It introduces a framework for integrating LLMs with existing preference elicitation schemes, addressing challenges like response variability and computational costs.
Findings
LLM proxies improve allocative efficiency by up to 20%
Results are consistent across different LLMs and report qualities
Framework effectively combines LLMs with preference elicitation methods
Abstract
We study the potential of large language models (LLMs) as proxies for humans to simplify preference elicitation (PE) in combinatorial assignment. While traditional PE methods rely on iterative queries to capture preferences, LLMs offer a one-shot alternative with reduced human effort. We propose a framework for LLM proxies that can work in tandem with SOTA ML-powered preference elicitation schemes. Our framework handles the novel challenges introduced by LLMs, such as response variability and increased computational costs. We experimentally evaluate the efficiency of LLM proxies against human queries in the well-studied course allocation domain, and we investigate the model capabilities required for success. We find that our approach improves allocative efficiency by up to 20%, and these results are robust across different LLMs and to differences in quality and accuracy of reporting.
Peer Reviews
Decision·Submitted to ICLR 2026
This paper introduces LLMs as low-effort, natural-language-based proxies for combinatorial PE. The idea is supported by solid empirical results, with up to 20% efficiency improvement and robustness across models.
This paper is evaluated on a course-allocation simulator, a well-established benchmark for non-monetary combinatorial assignment problems. The focus on fairness and welfare is consistent with this domain, and the absence of pricing or strategic bidding mechanisms is therefore within the paper’s intended scope. However, the evaluation could still benefit from broader validation. For example, by applying the framework to other assignment contexts, such as housing allocation or resource schedulin
1. The paper presents a standard solution, the user will present one structured query, and LLMs will do the iterative elicitation based on the query. The approach is natural and user-friendly, but quite well studied in the literature. The use of Double Thompson Sampling for efficient query selection that doubles performance versus alternatives, and epistemic MVNNs for uncertainty quantification, is nice. 2. The experimental evaluation is satisfactory. Testing robustness across multiple dimension
1. The novelty is not clear. There are several papers in the literature that use TS (or variants of TS) for query selection. Some ablation study are missing. 2. Theoretical Analysis is Shallow: Proposition 2.1 only provides a weak guarantee—that the true value function is a minimizer of expected GCE loss when accuracy >50%. This doesn't bound approximation error, convergence rate, or sample complexity. There's no analysis of how many queries are needed, how accuracy requirements scale with probl
+ The major motivation of the method is to address the issues faced by (a) the traditional structured reporting language, one-shot approach, and (b) iterative approaches. The proposed method utilizes one-shot natural language input, eliminating the need for users to employ structured reporting language. From natural language input, an LLM proxy can extract answers to answer comparison queries (CQs) that are implemented within the framework. This eliminates the need for users to manually answer
W1. I am not convinced that a one-shot input approach is appropriate. The one-shot input works when a user is very clear about what type of information is useful for the system to know. Assuming a user is new to the system and has no prior knowledge of what to enter, it would be beneficial to allow users to fine-tune their input through multiple iterations. In other cases, users may just not be sure what their preferences are, and they want to "add" more constraints after their initial input or
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Taxonomy
TopicsRough Sets and Fuzzy Logic · Data Management and Algorithms · Game Theory and Voting Systems
