Robust Robustness
Theoretical Economics
2026-05-06 v4
Abstract
We propose a refinement of the maxmin approach to robustness. A mechanism's payoff guarantee over an ambiguity set is \emph{robust} if the guarantee is approximately satisfied at priors near the ambiguity set (in the weak topology). We show that many maxmin-optimal mechanisms in the literature give payoff guarantees that are not robust. Such mechanisms are often tailored to degenerate worst-case priors, making them simple but fragile. Conversely, some commonly used ambiguity sets satisfy a structural property which ensures that every associated payoff guarantee is robust. We show how any ambiguity set can be slightly enriched to satisfy this property.
Cite
@article{arxiv.2408.16898,
title = {Robust Robustness},
author = {Ian Ball and Deniz Kattwinkel},
journal= {arXiv preprint arXiv:2408.16898},
year = {2026}
}