Money Market Fund

What Are Money Market Funds?

Money market funds (MMFs) are a type of mutual fund that invests in short-term, high-quality debt instruments such as Treasury bills, government agency securities, commercial paper, certificates of deposit, and repurchase agreements. They aim to maintain a stable $1.00 per share net asset value (NAV) while providing investors with liquidity and modest yield.

MMFs are one of the largest segments of the financial system, managing over $6 trillion in assets in the U.S. alone. They serve as a cash management tool for individuals, corporations, and institutional investors, sitting at the intersection of the banking and investment worlds.

Why It Matters for Markets

Money market funds play a critical role in short-term funding markets. Their purchases of commercial paper fund corporate working capital needs. Their repo investments provide financing for securities dealers. Their Treasury bill holdings help absorb government debt issuance. When MMF flows shift, the effects ripple through these interconnected markets.

The overnight reverse repo (ON RRP) facility at the Federal Reserve has become a massive parking spot for MMF cash. At its peak, over $2 trillion sat in the ON RRP, representing money that MMFs placed with the Fed rather than lending to the private sector. The gradual drawdown of ON RRP balances has been a key indicator of changing liquidity conditions.

For bank investors, MMF competition is a significant factor. When MMFs offer materially higher yields than bank deposit rates, deposits flow out of the banking system and into MMFs. This deposit migration forces banks to raise rates or find alternative funding, compressing net interest margins.

Post-Crisis Reforms

The 2008 money market crisis prompted sweeping reforms. The SEC now requires government MMFs to be separated from prime (credit) MMFs. Institutional prime MMFs must use floating NAVs rather than the fixed $1.00 price. Liquidity fees and redemption gates can be imposed during stress. These reforms reduced but did not eliminate the run risk inherent in MMF structures.

The 2023 banking stress saw record inflows into government money market funds as depositors sought higher yields and perceived safety. This migration highlighted the ongoing competitive dynamic between MMFs and bank deposits, and the systemic importance of money market funds in the modern financial ecosystem.