(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.