In Gross v. FBL Financial Services, Inc., 557 U.S. 167 (2009), the Supreme Court held 5-4 that an employee suing for age discrimination under the Age Discrimination in Employment Act must prove age was the “but-for” cause of the employer’s decision, not merely one factor among several. The ruling made age discrimination harder to prove than race or sex discrimination under Title VII, and the burden of persuasion never shifts to the employer at any point in the case.
What the Case Was About
Jack Gross joined FBL Financial Group in 1987 and worked his way up to Claims Administration Director. In 2003, when he was 54, FBL reassigned him to Claims Project Coordinator and moved most of his duties to a newly created position filled by a woman in her early forties.1Legal Information Institute. Gross v. FBL Financial Services FBL called it corporate restructuring. Gross called it a demotion because of his age and sued under the ADEA.
At trial, the judge told the jury that if Gross proved age was a motivating factor in the reassignment, the burden would shift to FBL to show it would have made the same decision anyway. The jury sided with Gross and awarded him lost compensation. The Eighth Circuit reversed, and the Supreme Court took the case to decide what evidence a plaintiff needs for that kind of mixed-motive instruction. Once there, the Court reframed the question and asked whether the mixed-motive framework applies to age claims at all.2Justia. Gross v. FBL Financial Services, Inc.
What the Court Held
The answer was no. Writing for the majority, Justice Thomas held that a plaintiff in an ADEA disparate-treatment case must prove by a preponderance of the evidence that age was the but-for cause of the challenged employment action. The plaintiff carries that burden the whole way through. It never shifts to the employer, even when the plaintiff shows age was one of several factors in the decision.2Justia. Gross v. FBL Financial Services, Inc.
The majority grounded that conclusion in the statute’s text. The ADEA forbids employers from acting “because of such individual’s age.”3U.S. Equal Employment Opportunity Commission. Age Discrimination in Employment Act of 1967 The ordinary meaning of “because of,” Thomas wrote, requires but-for causation. Age has to be the reason, not just a reason.
The Court also pointed to what Congress did, and did not do, after Price Waterhouse v. Hopkins. In the Civil Rights Act of 1991, Congress amended Title VII to say that an unlawful practice is established when a protected characteristic was “a motivating factor” in a decision, even if other factors also mattered.4GovInfo. 42 USC 2000e – Civil Rights Act Congress made no equivalent change to the ADEA. The majority read that silence as a choice: if Congress wanted the easier motivating-factor rule for age claims, it knew how to write it in.
How This Differs From Title VII Claims
The practical gap between age claims and most Title VII status-based claims is real. Under the motivating-factor test available for a Title VII race or sex claim, a plaintiff wins by showing the protected characteristic played a meaningful role in the decision, and the employer must then prove it would have made the same call anyway to limit remedies. Under the but-for test from Gross, the plaintiff must show the adverse action would not have happened had the employer set age aside. When several reasons were in play, some legitimate and some not, proving age was the decisive one is a steeper climb.
That does not mean a plaintiff needs a smoking gun. The Court said both direct and circumstantial evidence can establish but-for causation.2Justia. Gross v. FBL Financial Services, Inc. Age-related comments by decision-makers, statistical patterns in layoffs, and evidence that the employer’s stated reason is pretextual can all support the finding. What changes is who has to prove what: in an ADEA case, there is no moment where the employer must affirmatively prove its innocence.
The Dissent’s Objections
Justice Stevens wrote the principal dissent, joined by Justices Souter, Ginsburg, and Breyer. On the merits, Stevens argued that the ADEA’s “because of” language matches Title VII’s original text and should be read the same way. Price Waterhouse had interpreted that phrase in Title VII to reach mixed-motive claims, and Stevens saw no reason to give the identical phrase in the ADEA a different meaning. The 1991 amendments codified the motivating-factor rule for Title VII, in his view, but did not repudiate it for the ADEA.5U.S. Department of Justice. Gross v. FBL Financial Services – Supreme Court Decision
Justice Breyer wrote a separate dissent, joined by Souter and Ginsburg, on a more practical point. But-for causation, he argued, works for physical events but poorly for human motivation. When multiple considerations drive a decision, asking whether age was “the” cause instead of “a” cause forces the plaintiff into hypothetical reasoning that the employer is far better positioned to perform. That, Breyer said, is exactly why the burden should shift once the plaintiff shows age played a role.2Justia. Gross v. FBL Financial Services, Inc.
Where the But-For Rule Has Spread
Gross did not stay inside age law. In University of Texas Southwestern Medical Center v. Nassar (2013), the Supreme Court extended but-for causation to Title VII retaliation claims, reasoning that the anti-retaliation provision uses “because” the same way the ADEA does.6Justia. Univ. of Texas Southwestern Medical Center v. Nassar The result is a split inside Title VII itself: a claim that an employer fired you because of your race uses the motivating-factor test, but a claim that the same employer fired you for complaining about race discrimination uses the harder but-for test.
One boundary is worth flagging. In Babb v. Wilkie (2020), the Court held that the federal-sector provision of the ADEA is worded differently and does not require but-for causation for every form of relief. Federal employees can show age was a factor and still obtain certain remedies, though compensatory damages still require but-for proof. Gross continues to govern private-sector age claims.
What It Takes to Win an Age Case Now
For an employee weighing an ADEA lawsuit, the burden allocation matters more than the abstract legal standard. Because the plaintiff carries the burden throughout, building a documentary record before filing does much of the work: age-related remarks by decision-makers, shifting or inconsistent explanations from the employer, and comparisons showing younger colleagues in similar situations were treated differently. Most age cases turn on whether that evidence exists, not on how a court articulates the causation test.
Efforts to Undo the Ruling
Members of Congress have repeatedly introduced the Protecting Older Workers Against Discrimination Act, which would restore the mixed-motive framework for ADEA claims and let plaintiffs succeed by showing age was a motivating factor. The bill has been reintroduced in multiple sessions, most recently in 2025, and has never passed.7Congress.gov. Protecting Older Workers Against Discrimination Act of 2025 Unless and until Congress acts, the but-for standard from Gross remains the rule for private-sector age discrimination claims.