In McQuillan v. Southern Pacific Co. (1974) 40 Cal. App. 3d 802, the Court noted that a Public Employees' Retirement System pension benefit is " 'a derivative right, an element of the deceased's compensation earned by the employee by his performance of his duties. ' " ( Id. at pp. 807-808.) The contributions to the pension plan resulted in a collateral source benefit wholly independent from the tortfeasor.