The nation’s largest pension fund by assets said it has paid $3.4 billion in performance fees to private equity managers since 1990, providing the most significant disclosure yet in a debate at retirement plans over whether Wall Street is worth the price of admission.

The California Public Employees' Retirement System, known as Calpers, disclosed the performance-related expenses for the first time Tuesday. Calpers said those performance fees were based on profits of $24.2 billion earned in hundreds of private equity funds over the past 17 years.