Summary
- Non-seasonally adjusted inflation from September 2017 to March 2018 rose 1.11%, which creates the new annualized rate.
- Seasonally adjusted inflation in March actually dropped 0.1%, which was below expectations. Core inflation came in at 0.2%.
- Both ‘headline’ and core inflation are at one-year highs.
The variable rate on U.S. Series I Savings Bonds will fall from 2.48% to 2.22% for I Bonds purchased after May 1, based on the March inflation numbers just released by the U.S. Bureau of Labor Statistics.
Treasury Inflation-Protected Securities 
Note, "when you establish an account..." It does say "at any time" (perhaps someplace else?) Regs are tricky!