How does OPM establish and review post differentials?
Primary source
Verbatim text below is from the Electronic Code of Federal Regulations (eCFR), a public-domain U.S. government work. Always verify the current version with the eCFR before relying on it for any legal matter.
Full Text
(a) OPM establishes a post differential by rulemaking if Government agencies require it for recruitment purposes and if one or more of the following conditions exist:
(1) Extraordinarily difficult living conditions,
(2) Excessive physical hardship, and/or
(3) Notably unhealthful conditions.
(b) OPM periodically reviews with Federal agencies whether conditions of environment have changed in the post differential areas and whether payment of the post differential continues to be warranted as a recruitment incentive.
This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.