Pennsylvania’s largest pension fund has sued a key consulting firm that incorrectly calculated its investment profits. The lawsuit filed by the Public School Employees’ Retirement System (PSERS) says Chicago-based Aon Investments USA’s figures caused a costly error and contributed to the agency possibly facing federal investigators. Stakeholders for the 72-billion-dollar fund say the error was made to PSERS’ 2020 risk share analysis. They want to recover damages to compensate pension fund members for what they say is the “significant and ongoing harm” Aon has caused. The miscalculation by Aon, which tracks the system’s investments, resulted in certain school employees having to increase contributions to their pensions.