We provide a geometric proof that the random proposer mechanism is a 4-approximation to the first-best gains from trade in bilateral exchange. We then refine this geometric analysis to recover the state-of-the-art approximation ratio of 3.15.
Cite
@article{arxiv.2508.06469,
title = {A Geometric Analysis of Gains from Trade},
author = {Jason Hartline and Kangning Wang},
journal= {arXiv preprint arXiv:2508.06469},
year = {2025}
}