2. Bond prices and interest rates The remarkable thing about the events described in the article is that the yield on the 3-month T-bill was briefly negative. To see how this could happen, consider the relationship between bond prices and bond yields. A 3month Tbill with a maturity value of $1,000 is just a piece of paper that entitles the holder to $1,000 in three months. For example, if you were to buy a 3-month T-bill on September 24, 2008, with a maturity value of $1,000 and 90 days left to maturity, the U.S. government would pay you $1,000 on December 23, 2008. In general, the price of a bond is less than its maturity value. That is, if you are going to give up a certain amount of money for the duration of the bond, you expect to be paid for this loss of liquidity and compensated for inflation that could reduce the value of the repayment at the end of the period. Therefore, a piece of paper entitling you to $1,000 on December 23 would usually be worth less than $1,000 on September 24. The yield on a bond is a function of the percent by which your money implicitly grows while invested in it. In order to compare yields among bonds, yield is always reported as an annual interest rate. A bond's yield is a function of its maturity value (M), its price (PB), and the number of days until it matures. The general formula for the yield on a zero-coupon bond such as a T-bill is as follows: M 'P B X 360 M Days to Maturity Percentage Yield 2 100 X For example, if you were to pay $995 for a Tbill maturing in 90 days with a face value of $1,000, the percentage yield would be calculated as follows: $1,000$995 360 100 X $1,000 90 $5 100x m X4 100X0.005>