The Bonds That Fight the Monster Called Inflation - New York Times:
"The I Bonds offer a two-part interest-rate mechanism. The first is a fixed rate for the life of the bond. That rate is now 1 percent, applying to all I Bonds issued in the six months that started Nov. 1. The second rate is linked to the Consumer Price Index for urban consumers. This rate is reset twice a year - on Nov. 1 and May 1 - according to changes in the C.P.I.-U. It is this feature that has made the I Bond especially attractive to many fixed-income investors....On Nov. 1, the Treasury Department increased the variable I Bond rate to 5.70 percent - based on the climb in the inflation index from March to September - giving it a total annualized earnings rate of 6.73 percent.
"....And the rate looks even better when you consider that many observers...think that the C.P.I. overstates the real level of inflation in the economy."