The case of City of Los Angeles Department of Water and Power v. Manhart in 1977 revolved around gender discrimination in employment benefits. The Los Angeles Department of Water and Power required female employees to make larger contributions to the pension fund than their male counterparts, justifying this by citing actuarial tables that showed women generally live longer than men. However, several employees led by Joan Manhart challenged this practice as a violation of Title VII of the Civil Rights Act which prohibits sex-based discrimination in employment practices. The Supreme Court ruled in favor of Manhart et al., stating that while it is true on average women live longer than men, not every woman will outlive every man; thus making such generalizations for individuals was deemed unfair and unlawful under Title VII. It held that an employer cannot require higher contributions from one sex because statistically they are likely to receive more benefits due to longevity.

In the dissenting opinion for City of Los Angeles Department of Water and Power v. Manhart, Justice Rehnquist disagreed with the majority's interpretation of Title VII as prohibiting sex-based actuarial distinctions in pension plans. He argued that such a reading was inconsistent with Congress' intent when it enacted Title VII, which was to ensure equal opportunities rather than identical benefits for both sexes. According to him, using different mortality tables for men and women is not discriminatory but instead reflects biological realities; thus, requiring women to contribute more towards their pensions due to their longer life expectancy does not constitute discrimination under Title VII. Furthermore, he contended that this ruling could have unintended consequences by discouraging employers from offering defined benefit pension plans altogether or making them less generous overall.