31 CFR § 359.11 - What is the semiannual inflation rate?

---
identifier: "/us/cfr/t31/s359.11"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "31 CFR § 359.11 - What is the semiannual inflation rate?"
title_number: 31
title_name: "Money and Finance: Treasury"
section_number: "359.11"
section_name: "What is the semiannual inflation rate?"
chapter_name: "FISCAL SERVICE, DEPARTMENT OF THE TREASURY"
subchapter_number: "A"
subchapter_name: "BUREAU OF THE FISCAL SERVICE"
part_number: "359"
part_name: "OFFERING OF UNITED STATES SAVINGS BONDS, SERIES I"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "5 U.S.C. 301; 12 U.S.C. 391; 31 U.S.C. 3105."
regulatory_source: "67 FR 64278, Oct. 17, 2002, unless otherwise noted."
cfr_part: "359"
---


# 359.11 What is the semiannual inflation rate?

The index used to determine the semiannual inflation rate is the non-seasonally adjusted CPI-U (the Consumer Price Index for All Urban Consumers for the U.S. City Average for All Items, 1982-84 = 100) published by the Bureau of Labor Statistics of the U.S. Department of Labor. (For further information on CPI-U considerations, *see* appendix C to part 359 at section 1.) The semiannual inflation rate reflects the percentage change, if any, in the CPI-U over a six-month period. We announce this rate twice a year, in May and November. The semiannual inflation rate we announced in May 2002 reflects the percentage change between the CPI-U figures from the preceding March 2002 and September 2001. The rate of change over the six-month period, if any, will be expressed as a percentage, rounded to the nearest one-hundredth of one percent. More specifically, the semiannual inflation rate will be determined by the following formula (the resulting rate will be rounded to the nearest one-hundredth of one percent):

Semiannual inflation rate = (CPI − U<sub>Current</sub> − CPI − U<sub>Prior</sub>) ÷ CPI −U<sub>Prior</sub>