Abstract
This study establishes several facts about medieval monetary debasements: they were followed by unusually large minting volumes and by increased seigniorage; old and new coins circulated concurrently; and, at least some of the time, coins were valued by weight. These facts constitute a puzzle because debasements provide no additional inducements to bring coins to the mint. On theoretical and empirical grounds, the authors reject explanations based on by-tale circulation, nominal contracts, and sluggish price adjustment. They conclude that debasements pose a challenge to monetary economics.