I Put My Savings Into a Bond Fund. Then Rates Went Up.

The email came in at 11:47 on a Thursday night. A reader from Bangkok had written three sentences. “Ben. I did what you said. I bought a short-term bond fund. It’s down 7%. I thought bonds were safe.” I stared at the screen for a minute. He wasn’t wrong to be upset. He had done everything right. He had avoided the high-flying stock funds. He had picked something conservative. And now he was sitting on a loss that felt like it belonged to a completely different category of investment. I wrote him back. I told him I had made the same mistake. Not once. Twice.

I was in my early thirties when I first learned what duration actually means. I had bought a bond fund with an average maturity of eight years. The yield was decent. The manager had a good track record. I thought I was being responsible. Then the Federal Reserve started raising rates. The fund dropped 11% in four months. I called the fund company, confused. The person on the phone explained duration to me like I was a child. Every 1% rise in rates, a fund with an eight-year duration drops roughly 8%. I had never done that math. I had just assumed bond fund meant safe.

Here’s what I wish someone had explained to me with a step ladder. A bond fund is not a bond. A bond is a promise. You lend money, you get paid interest, you get your principal back at a fixed date. A bond fund is a ladder that never stops moving. The manager is constantly buying new rungs and selling old ones. If rates go up, the old rungs on the ladder lose value. You never get to the top and collect your principal because the top keeps moving. The fund never matures. That’s the feature they don’t put on the brochure.

I had a client in Hong Kong who retired in 2021. He put a huge chunk of his portfolio into a popular bond fund. The marketing materials called it “income-focused” and “defensive.” He didn’t need growth. He just needed steady checks. By the end of 2022, the fund was down 14%. The checks kept coming. But the principal he planned to leave to his kids was shrinking. He called me in tears. He said he had done everything right. He had stayed away from stocks. He had listened to his advisor. I told him the advisor should have explained duration. Most advisors don’t. They sell the story of income and hope the rate part doesn’t come up.

I keep a kitchen timer on my desk now. When someone pitches me a bond fund, I set it for the duration. If the duration is six years, I imagine the timer counting down. Every time the Fed hints at a rate move, I think about how much time is left on that timer. It’s not a perfect analogy. But it keeps me honest. I ask myself one question. Can I hold this fund for the full duration without panicking? If the answer is no, I don’t buy it. Not because it’s a bad fund. Because I know myself. I know I’ll check the price every day and convince myself I made a mistake.

The reader from Bangkok wrote me again last month. He had sold his short-term bond fund at a loss and moved everything into a money market fund. He said he couldn’t handle the volatility. I understood. I told him about my step ladder. I told him short-term funds are safer but not immune. A fund with a two-year duration can still drop 2% or 3% if rates move fast. That’s not a disaster. But if you’re not expecting any drop at all, it feels like a betrayal. The problem isn’t the fund. The problem is the expectation.

I use a sticky note on my screen when I’m looking at any bond fund. I write the duration on it. Then I write the yield. Then I divide the yield by the duration. That number tells me how much yield I’m getting for each year of interest rate risk. A fund yielding 5% with a duration of ten years gives me 0.5% per year of risk. A fund yielding 4% with a duration of two years gives me 2% per year of risk. The second fund is a better bet for me. I’m not saying it’s the right math for everyone. It’s just the math that keeps me from making the same mistake a third time.

I still own bond funds. I own a short-term fund with a duration under two years. I own a global fund that holds bonds in currencies I don’t have to think about. I don’t own any fund with a duration over five years. Not because I think rates are going up or down. Because I don’t want to explain to myself again why something I bought for safety is moving like something I bought for growth. The step ladder in my garage has a wobbly third rung. I know it’s there. I avoid it. I don’t pretend it’s stable just because I want it to be.

The reader hasn’t emailed me since that last exchange. I hope he’s okay with his money market fund. I hope he’s sleeping better. I think about him sometimes when I look at my own bond fund statements. I think about how we both learned the same lesson at different times. Safety is not a category. Safety is a set of numbers you actually understand. I don’t know if I’ll ever buy another long-term bond fund. I know I’ll never buy one without writing the duration on a sticky note first. That’s not a system. That’s just remembering what it felt like to be surprised.