The Consumer Price Index for All Urban Consumers (CPI-U) increased 0.2% in March on a seasonally adjusted basis, the U.S. Bureau of Labor Statistics reported this morning. This was slightly higher than the expected rate of 0.1%, and resulted in an inflation rate of 1.5% over the last 12 months.

Increases in the shelter and food indexes accounted for most of the increase. The food index increased 0.4% in March, with several major grocery. The energy index, in contrast, declined slightly in March, with gasoline down 1.7% and fuel oil down 2.9%. Utility gas service was up a strong 7.5%.

Excluding the volatile food and energy categories, core prices increased 0.2& in March and 1.7% in the past year.

Holders of TIPS and I Bonds are also interested in the non-seasonally adjusted CPI-U, which is used to determine the inflation adjustment on TIPS and the future inflation-adjusted interest rate on I Bonds. This number was up 0.6% in March, but the number for the last 12 months remains at 1.5%.

What this means for I Bonds. The March inflation number was the last piece needed to determine the inflation-adjusted variable rate for I Bonds that will begin May 1.

The inflation index at the end of March was 236.293, a 0.9156% increase over the 234.149 recorded at the end of September 2013. This should mean that the new I Bond inflation-adjusted rate will go to an annual rate of 1.83% or 1.84% for six months beginning May 1.

The annualized rate is currently 1.18%, plus a fixed rate of 0.2% that lasts as long as you hold the I Bond. We don’t know if the Treasury on May 1 will keep the fixed rate at 0.2%, drop it, or raise it. The Treasury does not provide a formula on how it makes this decision.

• Update: I Bond scenarios: Counting down to May 1, 2014