29 C.F.R. § 1620.14 : Labor — REGULATIONS RELATING TO LABOR — EQUAL EMPLOYMENT OPPORTUNITY COMMISSION — THE EQUAL PAY ACT — Testing equality of jobs

(a) In general. What constitutes equal skill, equal effort, or equal responsibility cannot be precisely defined. In interpreting these key terms of the statute, the broad remedial purpose of the law must be taken into consideration. The terms constitute separate tests, each of which must be met in order for the equal pay standard to apply. It should be kept in mind that "equal" does not mean "identical." Insubstantial or minor differences in the degree or amount of skill, or effort, or responsibility required for the performance of jobs will not render the equal pay standard inapplicable. On the other hand, substantial differences, such as those customarily associated with differences in wage levels when the jobs are performed by persons of one sex only, will ordinarily demonstrate an inequality as between the jobs justifying differences in pay. However, differences in skill, effort or responsibility which might be sufficient to justify a finding that two jobs are not equal within the meaning of the EPA if the greater skill, effort, or responsibility has been required of the higher paid sex, do not justify such a finding where the greater skill, effort, or responsibility is required of the lower paid sex. In determining whether job differences are so substantial as to make jobs unequal, it is pertinent to inquire whether and to what extent significance has been given to such differences in setting the wage levels for such jobs. Such an inquiry may, for example, disclose that apparent differences between jobs have not been recognized as relevant for wage purposes and that the facts as a whole support the conclusion that the differences are too insubstantial to prevent the jobs from being equal in all significant respects under the law.
(b) Illustrations of the concept. Where employees of opposite sexes are employed in jobs in which the duties they are required to perform and the working conditions are substantially the same, except that an employee of one sex is required to perform some duty or duties involving a higher skill which an employee of the other sex is not required to perform, the fact that the duties are different in this respect is insufficient to remove the jobs from the application of the equal pay standard if it also appears that the employer is paying a lower wage rate to the employee performing the additional duties notwithstanding the additional skill which they involve. In other situations, where employees of the opposite sex are employed in jobs which are equal in the levels of skill, effort, and responsibility required for their performance, it may be alleged that the assignment to employees of one sex but not the other of certain duties requiring less skill makes the jobs too different for comparison under the equal pay provisions. But so long as the higher level of skill is required for the performance of the jobs occupied by employees of both sexes, the fact that some of the duties assigned to employees of one sex require less skill than the employee must have for the job as a whole does not warrant any conclusion that the jobs are outside the purview of the equal pay standard.
(c) Determining equality of job content in general. In determining whether employees are performing equal work within the meaning of the EPA, the amounts of time which employees spend in the performance of different duties are not the sole criteria. It is also necessary to consider the degree of difference in terms of skill, effort, and responsibility. These factors are related in such a manner that a general standard to determine equality of jobs cannot be set up solely on the basis of a percentage of time. Consequently, a finding that one job requires employees to expend greater effort for a certain percentage of their working time than employees performing another job, would not in itself establish that the two jobs do not constitute equal work. Similarly, the performance of jobs on different machines or equipment would not necessarily result in a determination that the work so performed is unequal within the meaning of the statute if the equal pay provisions otherwise apply. If the difference in skill or effort required for the operation of such equipment is inconsequential, payment of a higher wage rate to employees of one sex because of a difference in machines or equipment would constitute a prohibited wage rate differential. Where greater skill or effort is required from the lower paid sex, the fact that the machines or equipment used to perform substantially equal work are different does not defeat a finding that the EPA has been violated. Likewise, the fact that jobs are performed in different departments or locations within the establishment would not necessarily be sufficient to demonstrate that unequal work is involved where the equal pay standard otherwise applies. This is particularly true in the case of retail establishments, and unless a showing can be made by the employer that the sale of one article requires such higher degree of skill or effort than the sale of another article as to render the equal pay standard inapplicable, it will be assumed that the salesmen and saleswomen concerned are performing equal work. Although the equal pay provisions apply on an establishment basis and the jobs to be compared are those in the particular establishment, all relevant evidence that may demonstrate whether the skill, effort, and responsibility required in the jobs in the particular establishment are equal should be considered, whether this relates to the performance of like jobs in other establishments or not.

29 C.F.R. § 1620.14