Breaking the Buck: When Money-Market Funds Fall Below $1 NAV

When a money-market fund’s net asset value (NAV) falls below $1.00 per share, the fund is said to have broken the buck — a rare but serious event that signals credit deterioration, rapid redemptions, or market stress within the fund’s portfolio. Most money-market funds maintain a stable $1.00 NAV through careful portfolio management and gate/fee structures; breaking the buck represents a breakdown in that stability.

How Money-Market Funds Maintain $1.00 NAV

A standard money-market fund is designed to offer investors a stable value—typically $1.00 per share—while providing modest income. This is achieved through conservative rules: holdings must mature within 13 months or less, credit quality must be high, and portfolio duration is kept very short.

Regulators mandate that fund managers value securities at amortized cost (a simplified accounting method) rather than market price, which insulates NAV from day-to-day market fluctuations. In a rising-rate environment, for example, the market value of a short-term bond might drop slightly, but amortized-cost accounting masks this loss. The fund absorbs small gains or losses in a separate reserve (the “capital support agency” arrangement), preserving the $1.00 share price for investors.

This protective mechanism works well in normal conditions. But when the underlying credit quality of the fund’s holdings deteriorates sharply or when liquidity risk surges, the $1.00 peg can break.

What Triggers a Break

Breaking the buck occurs when losses in the fund’s portfolio exceed its buffer. Three scenarios are most common:

Credit deterioration: A major money-market holding defaults or is downgraded unexpectedly. Early examples include the 2008 financial crisis, when the Reserve Primary Fund’s NAV fell to $0.97 after Lehman Brothers’ bankruptcy. The fund held commercial paper issued by Lehman; when it defaulted, the fund’s assets lost value faster than reserves could cover.

Redemption pressure: During market stress, investors redeem shares en masse, forcing the fund to liquidate holdings at unfavorable prices. If those holdings have declined in value, liquidation crystallizes losses. The fund may lack liquid reserves to meet redemptions at $1.00.

Operational or accounting shortfalls: In rare cases, accounting errors or misvaluation of holdings can cause NAV to slip below $1.00.

The Mechanics of Breaking

When NAV drops below $1.00, the fund is technically insolvent relative to its stated price. If NAV falls to $0.97, for example, an investor holding $10,000 in shares suddenly owns only $9,700 in assets.

The fund manager faces immediate choices:

• Absorb the loss with remaining capital: If the shortfall is very small, the fund can tap its reserve and attempt to restore NAV to $1.00 through income or recoveries.
• Gate redemptions or impose fees: Regulators allow fund boards to suspend redemptions or charge liquidity fees to stem the outflow and give the portfolio time to stabilize. These tools also protect long-term shareholders from subsidizing those who redeem first.
• Liquidate and wind down: In severe cases, the fund closes and distributes remaining assets to shareholders, locking in losses.

Post-2008 Regulatory Changes

The 2008 Reserve Primary Fund collapse prompted the SEC to tighten money-market fund rules substantially. In 2014 and again in 2019, the SEC introduced:

• Floating NAV for prime and tax-exempt funds: These funds now report NAV to four decimal places instead of maintaining an artificial $1.00 peg. This transparency reduces the incentive to redeem early before losses are realized.
• Government-only funds may retain a fixed $1.00 NAV if the board chooses, because they hold only Treasury bills, cash, and agency securities—the safest possible holdings.
• Liquidity fees and redemption gates: Boards can now charge fees (up to 2% per redemption) and suspend redemptions if the fund’s liquid assets fall below a threshold, buying time for stabilization.

These rules sharply reduced (though did not eliminate) the risk of breaking the buck. Since the overhaul, only a handful of funds have experienced NAV breaks, and they have typically been in specialized or higher-risk segments.

Distinguishing Breaking the Buck from Losses

It is important to note the difference between a normal fund loss and breaking the buck. All actively-managed funds and index funds can report negative returns in a given period—their NAV simply reflects the market value of their holdings. A bond fund might report a NAV of $9.50 in a rising-rate environment and investors accept this as a normal market outcome.

Breaking the buck, by contrast, refers specifically to a money-market fund—which is supposed to be stable at $1.00—falling below that target. It signals a failure of the protective mechanisms that govern money-market funds and is treated as a significant event.

Modern Risk Mitigation

Today, money-market funds are far safer than they were in the mid-2000s. Regulatory capital buffers, floating NAVs, liquidity tools, and tighter eligibility rules all work in concert. A Treasury-only or government money-market fund is, for practical purposes, as safe as holding Treasury bills directly, because the fund holds no credit risk.

Prime money-market funds (which hold corporate commercial paper and other short-term debt) face slightly higher risk but are still highly conservatively managed. The floating NAV also means losses are transparent—there is no artificial peg to break, only the true market value of holdings.

See also