5 U.S.C. § 5341

It is the policy of Congress that rates of pay of prevailing rate employees be fixed and adjusted from time to time as nearly as is consistent with the public interest in accordance with prevailing rates and be based on principles that— (1) there will be equal pay for substantially equal work for all prevailing rate employees who are working under similar conditions of employment in all agencies within the same local wage area; (2) there will be relative differences in pay within a local wage area when there are substantial or recognizable differences in duties, responsibilities, and qualification requirements among positions; (3) the level of rates of pay will be maintained in line with prevailing levels for comparable work within a local wage area; and (4) the level of rates of pay will be maintained so as to attract and retain qualified prevailing rate employees.