5 C.F.R. § 591.218 How does OPM compute price indexes?
Title 5 - Administrative Personnel
Except for shelter and energy utilities, OPM averages by item the prices collected in each survey area. For the Washington, DC, area, OPM computes a simple average for each item based on the average prices from each DC survey area. On an item-by-item basis, OPM divides the COLA survey area average price by the DC average price and produces a price index.
Title 5: Administrative Personnel
PART 591—ALLOWANCES AND DIFFERENTIALS
Subpart B—Cost-of-Living Allowance and Post Differential—Nonforeign Areas
Cost-of-Living Allowances
§ 591.218 How does OPM compute price indexes?
