There is a moment every bond investor eventually experiences. You open your brokerage account. You look at your bond fund. It is down.
Then you look at the cash or money-market fund sitting right next to it. It is paying interest.
So you ask the question that appears to have been written by common sense itself: why am I owning the thing that went down when the thing next to it is paying me 3%+ to do basically nothing?
Excellent question. In fact, it is such a good question that it can make a perfectly reasonable long-term investment strategy suddenly look ridiculous.
Why own a bond fund when a money-market fund is yielding 3%? Why accept price fluctuations when cash sits there at roughly $1 per share? Why watch your bond fund lose money when the cash fund sends a dividend every month?
And why, exactly, are we paying Wall Street to make our supposedly safe investment more complicated?
There is a catch. Actually, there are several.
The biggest one is that you are comparing something whose return changes very slowly with something whose return is essentially tied to what short-term interest rates are doing right now. Those are very different animals.
As of September 2026, for example, the Federal Reserve's target range for the federal funds rate is 3.75% to 4.00%. Vanguard's Federal Money Market Fund had a 7-day SEC yield of 3.74% on September 23. Meanwhile, Vanguard Total Bond Market ETF had a 30-day SEC yield around 4.7% in September, but its year-to-date NAV return had recently been negative.
That can look bizarre. The bond fund is earning interest. The cash fund is earning interest. One goes down. The other seems to sit there drinking tiny cups of coffee and collecting money.
What gives? The answer is that bond funds aren't just income machines. They are also constantly repricing the value of the bonds they own. And that little detail explains almost everything.