Stable NAV vs. Floating NAV Money Market Funds: What's the Difference?
A money market fund’s share price that never seems to move looks like a sign of stability, and in one important sense it is — but it also reflects a deliberate accounting choice, not a guarantee that the underlying assets never fluctuate in value at all.
The short answer
A stable net asset value (NAV) fund is structured and priced to maintain a constant share price, typically one dollar, even as the value of its underlying holdings shifts slightly day to day. A floating NAV fund instead lets its share price move with the actual market value of its holdings, the way most other mutual funds do. Which structure applies to a given fund depends largely on what it invests in and who is allowed to invest in it, following reforms that reshaped parts of the money market fund industry.
Where the stable NAV structure still applies
Government money market funds and funds sold to individual retail investors are generally permitted to keep using the stable NAV structure. These funds hold short-term, highly liquid securities and use accounting conventions that let the fund round its share price to a constant value under normal conditions. For a saver comparing government money market funds against other short-term options, the appeal of a stable NAV is largely practical: the number on the statement doesn’t move, which makes the fund feel and behave much like cash.
Where the floating NAV structure applies
Institutional prime and institutional municipal money market funds — generally those sold to large institutional investors rather than individual savers — are required to use a floating NAV instead. Their share price is calculated to more decimal places and moves in line with the actual value of the fund’s holdings, however small the daily movement might be. This change followed concerns, raised after periods of market stress, that a fixed one-dollar price could mask real fluctuations in a fund’s underlying value, particularly for funds holding corporate debt.
Why the distinction exists
The core issue is transparency versus convenience. A stable NAV is convenient for recordkeeping and gives the appearance of cash-like behavior, but it can obscure small day-to-day changes in a fund’s actual value. A floating NAV surfaces that movement directly, which regulators judged more appropriate for larger, more sophisticated investors in funds carrying somewhat more credit exposure. It’s a structural difference rather than a judgment about which fund is inherently a better place to hold savings; each structure suits a different type of investor and use case.
What this means for a typical saver
Most individual investors holding money market funds through a retail brokerage or bank sweep account are dealing with stable NAV funds, so the floating NAV distinction mainly becomes relevant for larger institutional cash management. Still, understanding the difference helps explain fund disclosures and why some money market fund share prices are quoted to four decimal places while others sit flatly at a round number, similar to how a brokered CD is priced and structured differently from a fund altogether.
The takeaway
Stable and floating NAV are two different ways of expressing the same underlying reality — a fund’s holdings change in value slightly from day to day. One approach smooths that number for convenience, the other reports it directly, and the rules for which structure a fund can use depend on its holdings and its intended investors, subject to regulations that can be revised over time.