Money market mutual funds are safer than stocks but riskier than bank savings accounts
A money market mutual fund invests in short-term debt — things like Treasury bills, commercial paper, and certificates of deposit that mature in less than a year. Because these investments are short-term and issued by stable borrowers (often the U.S. government or large corporations), the fund's value stays relatively stable. You will not see the wild swings you get with stock funds.
But "stable" does not mean "risk-free." The fund can lose money if the borrowers default, if interest rates move sharply, or if many investors withdraw at once. Your money is not insured by the FDIC the way a bank savings account is. The fund manager can also charge fees that eat into your returns. For most people, money market funds work best as a place to park cash temporarily — not as a long-term investment.
Key Takeaways
- Money market funds hold short-term debt from stable borrowers, so they fluctuate less than stock or bond funds, but they can still lose value.
- Your money is not protected by FDIC insurance, so if the fund's investments fail, you could lose some of what you invested.
- The fund's net asset value (NAV) can drop below $1 per share in rare cases, an event called "breaking the buck."
- Fees and interest rate changes both affect your returns, so comparing fund expense ratios matters even for seemingly low-risk investments.
- Money market funds are best used for emergency savings or cash you plan to use within months, not for money you need to grow over years.
How money market funds protect your principal
Money market funds reduce risk by holding only short-term, high-quality debt. A typical fund owns Treasury bills (backed by the U.S. government), commercial paper from large corporations, and bank CDs. Because these mature quickly — often within 90 days — the fund does not have to worry about long-term changes in the borrower's financial health. If a company's credit rating drops, the fund can straightforward let the investment mature and move the money elsewhere.
The fund also spreads money across many borrowers, so one default does not wipe out the whole fund. A fund might hold 100 or more different investments. Even if one borrower fails to repay, the impact on your share is tiny.
Fund managers also follow strict rules about what they can buy. The Securities and Exchange Commission (SEC) limits money market funds to investments rated in the top two credit categories. This means the fund cannot buy risky debt from struggling companies.
What can still go wrong with a money market fund
The biggest risk is that the fund's investments lose value or default. This is rare — money market funds have a long track record of stability — but it happens. In 2008, during the financial crisis, one large money market fund ("the Reserve Primary Fund") fell below $1 per share. Investors who had $10,000 in the fund lost about $40. The fund was forced to close.
A second risk is that many investors withdraw money at the same time. If thousands of people suddenly ask for their cash back, the fund may have to sell investments before they mature, possibly at a loss. During market panics, this can create a downward spiral: as the fund's value drops, more people withdraw, forcing more sales, dropping the value further.
Interest rate risk also matters. If interest rates rise, the value of the fund's existing investments falls (because new investments now pay more). If you need to withdraw before the investments mature, you may get less than you put in. This risk is small in money market funds because the investments are so short-term, but it is not zero.
Finally, fees reduce your returns. Even a fund charging 0.5% per year costs you money. If the fund is earning 4% but charging 0.5%, you keep 3.5%. Over time, that difference adds up.
The difference between money market funds and money market accounts
A money market account is a bank product, not a mutual fund. It works like a hybrid between a checking account and a savings account. The bank pays you interest and may let you write checks or use a debit card. The key difference: your money is insured by the FDIC up to $250,000 per depositor per bank.
A money market mutual fund offers no FDIC protection. If the fund fails, you could lose money. However, money market funds often pay higher interest rates than money market accounts because they take on more risk. A money market account at a bank might pay 4% to 5%, while a money market fund might pay 5% to 5.5% — but you give up the insurance.
For emergency savings or money you need within months, a money market account at a bank is usually safer. For larger amounts of cash you do not need when ready access to, a money market fund may make sense if the higher rate is worth the lack of insurance.
How to judge whether a specific money market fund is safe
Start by checking the fund's expense ratio — the annual fee as a percentage of your investment. You can find this in the fund's prospectus or on the fund company's website. For money market funds, anything under 0.25% is competitive. Funds charging 0.5% or more are expensive for this category.
Next, look at the fund's average maturity. This tells you how long, on average, until the fund's investments mature. A shorter average maturity (30 to 60 days) means less interest rate risk. A longer average maturity (90 days or more) means more risk if rates rise.
Check the fund's credit quality. The prospectus will say what percentage of the fund is in Treasury securities (safest), what percentage is in top-rated corporate debt, and what percentage is in lower-rated debt. A fund holding mostly Treasuries is safer than one holding mostly corporate paper.
Finally, look at the fund company's track record. Large, established firms like Vanguard, Fidelity, and Schwab have been managing money market funds for decades with few problems. Smaller or newer fund companies carry more risk straightforward because they have less experience and smaller assets to absorb losses.
When a money market fund makes sense for your situation
Money market funds work best as a temporary holding place for cash. If you have $50,000 you are saving for a down payment on a house in six months, a money market fund beats a regular savings account because it pays more interest. You are not trying to grow the money — you just want it to stay safe and earn something while you wait.
They also make sense if you have cash left over after investing in stocks and bonds and you want that cash to earn interest without taking on stock market risk. Some investors keep three to six months of living expenses in a money market fund as an emergency cushion.
Money market funds do not make sense as a long-term investment. If you have money you will not need for five years or more, stocks or bonds will likely earn more over that time, even accounting for their higher risk. Inflation will also eat away at the value of money sitting in a money market fund earning 4% or 5% per year.
Frequently Asked Questions
Can a money market fund go to zero?
Extremely unlikely, but technically possible. The fund would have to experience massive defaults across many of its investments at once. In practice, the worst case in recent history is the 2008 Reserve Primary Fund, which fell to $0.97 per share — a loss of 3%, not a total wipeout. The SEC has since tightened rules to make this even less likely.
Is my money in a money market fund insured?
No. FDIC insurance only covers bank deposits, not mutual funds. If you want insurance protection, use a money market account at a bank instead. The tradeoff is that bank accounts usually pay lower interest rates.
What happens if interest rates go up after I invest?
The fund's existing investments become less valuable because new investments now pay more. However, because money market funds hold only short-term debt, this effect is small. Your investments will mature soon, and the fund will reinvest the money at the new, higher rates. You will not see the big losses that bond funds experience when rates rise.
Should I choose a government money market fund or a general money market fund?
A government money market fund holds mostly Treasury bills and other U.S. government debt, so it is safer but usually pays less interest. A general money market fund holds a mix of government and corporate debt, so it pays more but carries slightly more risk. For most people, a general fund is the better choice because the extra risk is small and the extra interest is real.
How do I compare money market funds from different companies?
Look at three things: expense ratio (lower is better), average maturity (shorter is safer), and credit quality (more Treasuries is safer). Also check the fund's seven-day yield, which shows what you would earn if the current interest rate stayed the same for a year. Higher yield is better, but not if it comes from taking on much more risk.