Inflation-Indexed Bond

Inflation-indexed bonds (also known as inflation-linked bonds or colloquially as linkers) are bonds where the principal is indexed to inflation. They are thus designed to cut out the inflation risk of an investment. The first known inflation-indexed bond was issued by the Massachusetts Bay Company in 1780. The market has grown dramatically since the British government began issuing inflation-linked Gilts in 1981. As of 2008, government-issued inflation-linked bonds comprise over $1.5 trillion of the international debt market. The inflation-linked market primarily consists of sovereign debt, with privately issued inflation-linked bonds constituting a small portion of the market.

Structure

Inflation-indexed bonds pay a coupon that is equivalent to the sum of the increase in an inflation index and the real coupon rate. The relationship between coupon payments, breakeven inflation and real interest rates is given by the Fisher equation. A rise in coupon payments is a result of an increase in inflation expectations, real rates, or both.

A common misconception about these bonds is that the interest rate changes with inflation. What actually happens is that the underlying principal of the bond changes, which results in a higher interest payment when multiplied by the same rate. For example, if the coupon of an annual bond was 5% and the underlying principal of the bond was 100 units, the annual payment would be 5 units. If the inflation index increased by 10%, the principal of the bond would increase to 110 units. The coupon rate would remain at 5%, resulting in an interest payment of 110 x 5% = 5.5 units. The only known exception to this is the Australian Capital Indexed Bond, in which the interest rate is adjusted as well as the principal.

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