Many workers choose the bond fund in their 401(k) for stability. Bonds generally swing less than stocks, and they pay regular income. But a bond fund is not a savings account, and in a year when the Federal Reserve has raised rates, participants may notice that "safer" does not mean "steady." Understanding why can help savers choose with open eyes.
The Basic Seesaw
Bond prices and interest rates move in opposite directions. The SEC's Office of Investor Education and Advocacy explains that when market rates rise, the price of an existing fixed-rate bond falls, a risk that applies to all bonds, including U.S. Treasuries. The reason is straightforward. A bond paying 3 percent is less attractive when new bonds pay 4 percent, so its price must drop to compete.
The bulletin gives a worked example. A 3 percent bond bought at $1,000 would rise in price to $1,082 if rates fell to 2 percent and drop to $925 if rates rose to 4 percent. The numbers are illustrative of one bond's behavior, not a forecast, and the exact amounts depend on the maturity.
Duration: The Yardstick
How much a bond fund moves depends heavily on its duration. FINRA, the securities industry's self-regulator, describes duration as a measure of how sensitive a bond investment is to interest rate changes. Duration is not the same as maturity. As a rule of thumb, for each one-percentage-point change in rates, the price should move in the opposite direction by roughly the duration number, in percent. A duration of 10, for example, implies about a 10 percent price decline if rates rise by one point.
Here is a hypothetical case. A participant holds $50,000 in a bond fund with a duration of 6. If rates rose one percentage point, the fund's price might fall by about 6 percent, or around $3,000, all else equal. A one-point decline in rates would have the opposite effect. Interest income paid by the fund partly offsets price changes, so the total return can differ from the price move.
Participants can usually find a fund's duration on its fact sheet or prospectus, which many plans provide online.
Why the Current Backdrop Matters
The rate environment has shifted this year. The Fed raised its target range to 3.75 to 4 percent in September, the first increase since 2023, according to Cointelegraph's report, and held it there on October 28, as its statement shows. Longer-term yields are higher still: the Treasury reported a 10-year yield of 4.94 percent on October 30 and a 30-year yield of 5.31 percent (Treasury data).
Higher yields cut both ways. Existing bondholders may see price declines when rates rise. But those who keep buying, including through ongoing paycheck contributions, purchase new bonds at higher yields, and the SEC notes that an investor who holds a bond to maturity receives the stated interest and face value. A bond fund has no fixed maturity, so that comfort is less direct for fund investors, and the fund's value can stay below earlier levels until yields or the portfolio changes.
Other Options Inside a Plan
Plans differ, but many offer more than one fixed-income choice. These may include a money market fund, a stable value fund, a short-term bond fund, an intermediate or total bond index fund, and target-date funds, which hold a mix of stocks and bonds that adjusts over time. Short-term funds generally have lower duration and smaller price swings, though they usually offer lower income than longer-term funds when the curve slopes upward. Stable value and money market options have their own features and risks, and they are not insured like bank deposits, so participants should read the plan's fund descriptions.
Questions Worth Asking
- What is the fund's duration and average maturity? A higher number means greater sensitivity to rates.
- What is the credit quality? Funds holding lower-rated bonds add default risk on top of interest rate risk.
- What role does the bond fund play? A participant with decades until retirement may weigh price swings differently from someone planning withdrawals in a few years.
- What do the fees look like? Expense ratios are listed in the plan's disclosures and reduce returns over time.
Keep the Rate Story in Proportion
Interest rate risk is only one factor in a retirement portfolio. Rate moves are hard to predict, and the Fed has said its future decisions depend on incoming data. Reshuffling a 401(k) on a single rate headline can create its own costs. Many savers are better served by matching holdings to their time horizon and checking them on a set schedule, and a plan's fiduciary materials or a qualified professional can help.
This article is for informational and educational purposes only and should not be considered personalized financial, investment, or tax advice.
