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| Format: | Preprint |
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2026
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| Online Access: | https://arxiv.org/abs/2605.16780 |
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| _version_ | 1866910225807704064 |
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| author | Yu, Jiguang |
| author_facet | Yu, Jiguang |
| contents | Hierarchical decision problems are often modeled as bilevel programs in which a leader commits to a policy and a follower responds optimally. When the follower's optimal response is nonunique, or when only near-optimal follower behavior can be verified, the same leader decision may induce a range of upper-level outcomes. This paper develops a diagnostic framework for quantifying that exposure. For a leader decision $x$, we evaluate the optimistic and pessimistic upper-level values over the $ε$-optimal follower response set $S_ε(x)$ and use their difference, \[
Δ_ε(x):=ψ_ε^p(x)-ψ_ε^o(x), \] as an ambiguity premium. The premium itself is classical in the optimistic--pessimistic bilevel distinction; the contribution here is to make it operational as an implementation-risk diagnostic. We establish a diameter bound $Δ_ε(x)\le L_F(x)\,\mathrm{diam}(S_ε(x))$ and an $\mathcal{O}(\sqrtε)$ estimate under quadratic lower-level growth. We then organize existing bilevel--GNEP reformulations by their computational roles and propose a screening workflow that reports, for each candidate policy, nominal value, ambiguity exposure, and a first-order residual. Two stylized case studies -- a parallel-link Stackelberg pricing problem and a convex generation-planning model with diversification constraints -- show how the resulting robustness--efficiency frontier can identify policies that are nominally attractive but sensitive to near-optimal follower responses. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_16780 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | A Diagnostic Framework for Implementation Risk in Bilevel Decision Problems: The Ambiguity Premium and the Robustness--Efficiency Frontier Yu, Jiguang Optimization and Control Hierarchical decision problems are often modeled as bilevel programs in which a leader commits to a policy and a follower responds optimally. When the follower's optimal response is nonunique, or when only near-optimal follower behavior can be verified, the same leader decision may induce a range of upper-level outcomes. This paper develops a diagnostic framework for quantifying that exposure. For a leader decision $x$, we evaluate the optimistic and pessimistic upper-level values over the $ε$-optimal follower response set $S_ε(x)$ and use their difference, \[ Δ_ε(x):=ψ_ε^p(x)-ψ_ε^o(x), \] as an ambiguity premium. The premium itself is classical in the optimistic--pessimistic bilevel distinction; the contribution here is to make it operational as an implementation-risk diagnostic. We establish a diameter bound $Δ_ε(x)\le L_F(x)\,\mathrm{diam}(S_ε(x))$ and an $\mathcal{O}(\sqrtε)$ estimate under quadratic lower-level growth. We then organize existing bilevel--GNEP reformulations by their computational roles and propose a screening workflow that reports, for each candidate policy, nominal value, ambiguity exposure, and a first-order residual. Two stylized case studies -- a parallel-link Stackelberg pricing problem and a convex generation-planning model with diversification constraints -- show how the resulting robustness--efficiency frontier can identify policies that are nominally attractive but sensitive to near-optimal follower responses. |
| title | A Diagnostic Framework for Implementation Risk in Bilevel Decision Problems: The Ambiguity Premium and the Robustness--Efficiency Frontier |
| topic | Optimization and Control |
| url | https://arxiv.org/abs/2605.16780 |