CFR > Title 5 - Administrative Personnel > CHAPTER I—OFFICE OF PERSONNEL MANAGEMENT > SUBCHAPTER B—CIVIL SERVICE REGULATIONS (parts 110 to 990) > PART 591—ALLOWANCES AND DIFFERENTIALS > SUBPART B—Cost-of-Living Allowance and Post Differential—Nonforeign Areas (§591.201 to §591.244) > 591.209—What is a price index?

591.209—What is a price index?

(a) The price index is the COLA area price divided by the DC area price and multiplied by 100.
(b) Example:
COLA Area Average Price for Item A = $1.233
DC Area Average Price for Item A = $1.164
Computation:
$1.233/$1.164 = 1.0592783
1.0592783 × 100 = 105.92783.
(c) In the case of the final index, OPM rounds the index to two decimal places.