Actuarial Notes

Spot Rate

Study guide: Exam FM-2

The n-year spot rate s_n is the yield to maturity on a zero-coupon bond that matures in exactly n years, representing the market's required return for a single cash flow received at time n with no intermediate payments. A coupon bond is priced by discounting each cash flow at the spot rate for that maturity:

P = \sum_{t=1}^{n} \frac{C_t}{(1+s_t)^t}

  • Spot rates are read from the Yield Curve or bootstrapped from observed bond prices
  • The relationship between spot rates and forward rates is (1+s_n)^n = (1+s_{n-1})^{n-1}(1+f_{n-1,n}), where f_{n-1,n} is the one-year forward rate from year n-1 to n

Pricing a Bond with Spot Rates Spot rates are s_1 = 4\%, s_2 = 5\%, s_3 = 6\%. Find the price of a $1{,}000 face value 3-year bond paying annual coupons of $60.

Answer Discount each cash flow at the corresponding spot rate: P = \frac{60}{1.04} + \frac{60}{1.05^2} + \frac{1060}{1.06^3} P = 57.69 + 54.42 + 890.00 = \$1{,}002.11 Note this differs from using a single flat yield, because the spot curve is upward-sloping (longer maturities have higher rates).