The composite interest rate accrued by U.S. Treasury Series I bonds issued from November 1, 2014 to April 30, 2015 is 1.48 percent. The rate of return for Series I bonds is typically significantly lower than riskier investments such as stocks and corporate bonds.
Series I bonds are debt securities issued by the U.S. Department of Treasury and essentially function as a loan to the government. The interest on a Series I bond is compounded semi-annually, so the interest accrued is added to the principal value on the six and 12-month anniversaries of the bond purchase. Series I bonds earn interest for up to 30 years after issuance.