ADEA@40 (1997 - 2007): The Supreme Court identifies differences between the ADEA and Title VII that narrow the ADEA's reach.
In Kimel v. Florida Bd. of Regents, 528 U.S. 62 (2000), the Supreme Court holds that state sovereign immunity under the 11th Amendment of the U.S. Constitution prevents older workers from suing states for damages under the ADEA.
In General Dynamics Land Systems, Inc. v. Cline, 540 U.S. 581 (2004), the Court distinguishes the ADEA's coverage of "age" from Title VII's coverage of race or sex, by construing the ADEA to conclude that it does not prevent an employer from favoring an older employee over a relatively younger one, even if both are covered by the ADEA.
In Smith v. City of Jackson, Mississippi, 544 U.S. 228 (2005), the Supreme Court acknowledges the similarities in the ADEA's and Title VII's prohibitions and holds that the ADEA permits disparate-impact claims. However, the Court also distinguishes the employer's defense in such cases. Given textual differences between the ADEA and Title VII, the Court finds that the language of the ADEA permits adverse impacts that are based on a reasonable factor other than age.