Competition Complexity in Multi-Item Auctions: Beyond VCG and Regularity

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Hauptverfasser: Beyhaghi, Hedyeh, Cai, Linda, Feng, Yiding, Li, Yingkai, Weinberg, S. Matthew
Format: Preprint
Veröffentlicht: 2025
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author Beyhaghi, Hedyeh
Cai, Linda
Feng, Yiding
Li, Yingkai
Weinberg, S. Matthew
author_facet Beyhaghi, Hedyeh
Cai, Linda
Feng, Yiding
Li, Yingkai
Weinberg, S. Matthew
contents We quantify the value of the monopoly's bargaining power in terms of competition complexity--that is, the number of additional bidders the monopoly must attract in simple auctions to match the expected revenue of the optimal mechanisms (c.f., Bulow and Klemperer, 1996, Eden et al., 2017)--within the setting of multi-item auctions. We show that for simple auctions that sell items separately, the competition complexity is $Θ(\frac{n}α)$ in an environment with $n$ original bidders under the slightly stronger assumption of $α$-strong regularity, in contrast to the standard regularity assumption in the literature, which requires $Ω(n \cdot \ln \frac{m}{n})$ additional bidders (Feldman et al., 2018). This significantly reduces the value of learning the distribution to design the optimal mechanisms, especially in large markets with many items for sale. For simple auctions that sell items as a grand bundle, we establish a constant competition complexity bound in a single-bidder environment when the number of items is small or when the value distribution has a monotone hazard rate. Some of our competition complexity results also hold when we compete against the first best benchmark (i.e., optimal social welfare).
format Preprint
id arxiv_https___arxiv_org_abs_2506_09291
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Competition Complexity in Multi-Item Auctions: Beyond VCG and Regularity
Beyhaghi, Hedyeh
Cai, Linda
Feng, Yiding
Li, Yingkai
Weinberg, S. Matthew
Computer Science and Game Theory
Theoretical Economics
We quantify the value of the monopoly's bargaining power in terms of competition complexity--that is, the number of additional bidders the monopoly must attract in simple auctions to match the expected revenue of the optimal mechanisms (c.f., Bulow and Klemperer, 1996, Eden et al., 2017)--within the setting of multi-item auctions. We show that for simple auctions that sell items separately, the competition complexity is $Θ(\frac{n}α)$ in an environment with $n$ original bidders under the slightly stronger assumption of $α$-strong regularity, in contrast to the standard regularity assumption in the literature, which requires $Ω(n \cdot \ln \frac{m}{n})$ additional bidders (Feldman et al., 2018). This significantly reduces the value of learning the distribution to design the optimal mechanisms, especially in large markets with many items for sale. For simple auctions that sell items as a grand bundle, we establish a constant competition complexity bound in a single-bidder environment when the number of items is small or when the value distribution has a monotone hazard rate. Some of our competition complexity results also hold when we compete against the first best benchmark (i.e., optimal social welfare).
title Competition Complexity in Multi-Item Auctions: Beyond VCG and Regularity
topic Computer Science and Game Theory
Theoretical Economics
url https://arxiv.org/abs/2506.09291