The fundamental inverse relationship between interest rates and bond prices — and why this is the most important concept in fixed income.
In this lesson you'll learn
The inverse relationship between rates and prices — and why it's inevitable
How to reason through price moves from first principles
Why the 2022 bond market crash happened — and what it means
Why long bonds are riskier than short bonds in rising-rate environments
Real vs nominal rates, and how TIPS and I-Bonds protect against inflation
The Inverse Relationship — The Most Important Bond Rule
When interest rates go up → bond prices go down
When interest rates go down → bond prices go up
This inverse relationship is the single most important concept in fixed income. Understanding why it happens makes everything else in bonds click. It's not a coincidence — it's a mathematical inevitability.
Bonds and interest rates are like opposite ends of a seesaw. They cannot both move in the same direction at the same time. Every bond pricing model, every duration calculation, and every yield curve analysis flows from this one relationship.
Why Prices Must Move — The Logic
Here's the intuition. You own a bond paying a 5% coupon ($50/year). The Fed raises rates; new bonds now pay 6% ($60/year).
Your old 5% bond is now less attractive. Why would anyone pay $1,000 for it when new bonds pay $60 instead of $50? They won't — unless you lower your price so the effective yield matches the new 6% rate.
The price must fall to approximately $833 (where $50/$833 ≈ 6%). Your bond didn't get riskier — the market simply repriced it to match current rates. This is purely mechanical.
The math is simple: current yield = coupon ÷ price. For the yield to go UP, the price must go DOWN. For the yield to go DOWN, the price must go UP. They always move in opposite directions. This is not policy or convention — it's arithmetic.
Real Example — The 2022 Bond Crash
2022 was the worst year for bonds in modern history. The US Federal Reserve raised interest rates from 0.25% to 4.5% — one of the fastest hiking cycles ever recorded. The consequences were severe:
Long-Term Treasuries (20+ yr)
→TLT ETF dropped from ~$150 to ~$100
→~30% price decline in a single year
→Worst performance in over 100 years
→Shocked retirees who thought bonds were 'safe'
Short-Term Treasuries (1–3 yr)
Fell only 3–5% in 2022
Matured quickly, returning par value
Investors rolled into higher-yielding new bonds
Far better performance than long bonds
The critical lesson from 2022: bonds protect against credit risk and stock market crashes — but they do NOT protect against interest rate risk. Rising rates hurt long-term bonds severely. This is why maturity selection matters so much.
Short-term bonds fell only 3–5% in 2022 — far less than stocks (S&P 500 was down ~18%) and far less than long bonds. This shows why duration management is central to bond investing. (Duration is the topic of Lesson 4.)
Real Interest Rates vs Nominal
Inflation erodes the purchasing power of bond returns. A 5% nominal yield with 4% inflation delivers only 1% real return — and on a 30-year bond, that difference is enormous.
The principal adjusts upward with CPI. If you hold a $1,000 TIPS and inflation runs at 5%, your principal grows to $1,050 — and your coupon (based on adjusted principal) also grows. Real yield is locked in at issuance regardless of inflation. In high-inflation periods, TIPS outperform nominal Treasuries significantly.
I-Bonds (Series I Savings Bonds)
Inflation-linked rate resets every 6 months based on CPI data. Purchase limit: $10,000/year per person ($5,000 more via tax refund). Cannot redeem in the first 12 months. 3-month interest penalty if redeemed before 5 years. In low-inflation periods, regular Treasuries often do better than I-Bonds.
Inflation Environment
Regular Treasuries
TIPS / I-Bonds
High inflation (4%+)
Real return shrinks
Principal adjusts — real return protected
Low inflation (1–2%)
Full nominal return captured
Lower yield premium than regular Treasuries
Deflation
Real return actually increases
Principal doesn't fall below original issue price
Quick Knowledge Check
3 questions · test what you've just learned
1
The Federal Reserve raises interest rates by 1%. What happens to existing bond prices?
2
Why did long-term Treasury bonds fall ~30% in 2022 while short-term Treasury bills fell very little?
3
A TIPS (Treasury Inflation-Protected Security) differs from a regular Treasury because:
✓ Key takeaways from Lesson 3
The fundamental rule: when interest rates rise, bond prices fall — and vice versa. This is arithmetic, not policy.
Why: existing bonds must reprice so their effective yield matches new market rates.
2022 example: Fed raised rates from 0.25% to 4.5% → long Treasuries fell ~30%, short T-Bills fell 3–5%.
Bonds protect against credit risk and stock crashes — but NOT against interest rate risk.
TIPS and I-Bonds protect against inflation by adjusting principal with CPI. Best used in high-inflation periods.