Abstract
We study the problem of fairly and efficiently allocating a set of items among strategic agents with additive valuations, where items are either all indivisible or all divisible. When items are goods, numerous positive and negative results are known regarding the fairness and efficiency guarantees achievable by truthful mechanisms, whereas our understanding of truthful mechanisms for chores remains considerably more limited. In this paper, we discover various connections between truthful good and chore allocations, greatly enhancing our understanding of the latter via tools from the former.
For indivisible chores with two agents, by leveraging the observation that a simple bundle-swapping operation transforms several properties for goods including truthfulness to the corresponding properties for chores, we characterize truthful mechanisms and derive tight guarantees of various fairness notions achieved by truthful mechanisms. Moreover, for homogeneous divisible chores, by generalizing the above transformation to an arbitrary number of agents, we characterize truthful mechanisms with two agents, show that every truthful mechanism with two agents admits an efficiency ratio of 0, and derive a large family of strictly truthful, envy-free (EF), and proportional mechanisms for an arbitrary number of agents. Finally, for indivisible chores with an arbitrary number of agents having bi-valued cost functions, we give an ex-ante truthful, ex-ante Pareto optimal, ex-ante EF, and ex-post envy-free up to one item mechanism, improving the best guarantees for bi-valued instances by prior works.
The full version of our paper is available on arXiv: https://arxiv.org/abs/2505.01629.
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Notes
- 1.
Consider the case with two agents and one item.
- 2.
Restricted additive valuations constitute a strict superset of binary valuations and a strict subset of additive valuations.
- 3.
Note that ex-ante PO implies ex-post fPO.
- 4.
Here, we encode a utility function \(v_j\) by the vector \((v_j(o_1), \ldots , v_j(o_m)) \in [0, 1]^m\), and we say that a condition holds with respect to a utility function if it holds with respect to the corresponding vector in \([0, 1]^m\).
- 5.
- 6.
When \(q = 0\), the case of bi-valued cost functions are equivalent to that of binary cost functions, which has been thoroughly studied by prior work, e.g., [48].
- 7.
We say that the cost functions are restricted additive if each item o is associated with an intrinsic value \(e_o\) such that \(c_i(o) \in \{0, e_o\}\) for every agent i.
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Acknowledgments
We would like to thank the anonymous reviewers for their detailed feedback and comments that helped significantly improve the exposition of this paper. Bo Li is partly funded by the Hong Kong SAR Research Grants Council (No. PolyU 15224823) and the Department of Science and Technology of Guangdong Province (No. 2023A1515010592). The research of Biaoshuai Tao is supported by the National Natural Science Foundation of China (No. 62472271) and the Key Laboratory of Interdisciplinary Research of Computation and Economics (Shanghai University of Finance and Economics), Ministry of Education. Xiaowei Wu is funded by the Science and Technology Development Fund (FDCT), Macau SAR (file no. 0147/2024/RIA2, 0014/2022/AFJ, 0085/2022/A, and 001/2024/SKL).
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Li, B., Tao, B., Wang, F., Wu, X., Yang, M., Zhou, S. (2026). When is Truthfully Allocating Chores No Harder Than Goods?. In: Lavi, R., Zhang, J. (eds) Algorithmic Game Theory. SAGT 2025. Lecture Notes in Computer Science, vol 15953. Springer, Cham. https://doi.org/10.1007/978-3-032-03639-1_14
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