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Field Guide › Bonds course › Lesson 1

Bonds course · Lesson 1 of 7

When rates go up, bond prices go down.

A bond pays fixed interest. When the market pays more for new bonds, the price of an old bond must fall. This lesson shows how far, and why.

EDUCATION, NOT ADVICE · The example bonds. The yields, spreads and inflation rates in this course are examples, not forecasts. The I bond rates and the 2026 tax brackets are real, and the sources say where they come from. A model script calculates every figure. Full disclosures →

The example bond

The example bond has a face value of $1,000, a coupon of 4% and 10 years to maturity. It pays two coupons a year, of $20 each. At maturity, it repays the $1,000.

The coupons and the repayment never change. Only the price changes.

The price at each yield

Market yieldPriceChange from face valueCurrent yield
2%$1,180.46+18.0%3.39%
3%$1,085.84+8.6%3.68%
4%$1,000.00-0.0%4.00%
5%$922.05-7.8%4.34%
6%$851.23-14.9%4.70%

When the market yield equals the coupon, the bond sells at its face value. When new bonds pay 5%, nobody pays $1,000 for a bond that pays 4%. The price falls to $922.05, and at that price the bond gives 5% a year.

Two yields

Current yield is the yearly coupon divided by the price. At a price of $922.05, it is 4.34%.

Yield to maturity also counts the gain at maturity. A buyer at $922.05 gets back $1,000, which is $77.95 more. Coupons plus that gain give 5% a year. When the price is below face value, current yield is lower than yield to maturity.

The curve is not a straight line

A fall of 1 point in the yield adds $85.84 to the price. A rise of 1 point takes away $77.95. The gain is larger than the loss. Lesson 2 shows why.

Key points

  • A bond pays fixed coupons and repays its face value. Only the price changes.
  • When market yields go up, bond prices go down, until the yield matches the market.
  • Yield to maturity counts the coupons and the gain or loss at maturity.

Sources

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