In many matching environments, agreements are multilateral and/or have externalities. We show that stability in these environments depends on agents' aggregate choice behavior. Two different conditions on aggregate choice ensure a stable outcome exists. One applies when contracts are...

In this paper, we show that stable outcomes exist in matching environments with complementarities, such as social media platforms or markets for patent licenses. Our results apply to both nontransferable and transferable utility settings, and allow for multilateral agreements and those with...