In 1967, Congress enacted the Age Discrimination in Employment Act, also called the ADEA. In its current iteration, the ADEA provides:
It shall be unlawful for an employer—
(1) to fail or refuse to hire or to discharge any individual or otherwise discriminate against any individual with respect to his compensation, terms, conditions, or privileges of employment, because of such individual’s age;
(2) to limit, segregate, or classify his employees in any way which would deprive or tend to deprive any individual of employment opportunities or otherwise adversely affect his status as an employee, because of such individual’s age; or
(3) to reduce the wage rate of any employee in order to comply with this chapter.
29 U.S.C. § 623(a). The ADEA also contains some very important language of limitation: “It shall not be unlawful for an employer, employment agency, or labor organization—(1) to take any action otherwise prohibited under subsections (a) . . . where the differentiation is based on reasonable factors other than age.” 29 U.S.C. § 623(f)(1). Courts refer to this latter provision as the “reasonable factor other than age” (RFOA) provision.
Enacted just three years after Title VII, the ADEA’s first two operative provisions are very similar to Title VII’s main provisions. Indeed, throughout the first decades of these statutes’ enforcement, the courts tended to read the two statutes in a similar way. If a court developed a proof structure for Title VII, courts would also use that same proof structure for ADEA claims. But, in the last two decades, the Supreme Court has interpreted the ADEA discrimination provisions to require different proof structures than those used under Title VII. It is no longer safe to assume that a concept that applies in the Title VII context also applies to the ADEA.