Money Market Funds (MMFs), which are crucial to short-term funding markets, rely on voluntary support of fund sponsors to maintain stable share values. I develop a general equilibrium model of MMFs to study how sponsor support affects the industry's fragility and regulation. Adverse...

I develop a model of money market funds (MMFs) to study the ability of sponsor support to provide stability to the industry. I find that strategic complementarities in the sponsors' support decisions can make MMFs vulnerable to runs different from the canonical bank-runs: it may lead to runs of...