The California Public Employees’ Retirement System, best known as Calpers, is the largest pension system in the U.S. by assets. A recent securities filing shows the agency made key changes to its holdings from the second and third quarters. Calpers filed a Form 13F with the Securities and Exchange Commission on Nov. 14 showing it took a stake in Bloom Energy through the purchase of 361,883 shares, worth $30.6 million at the time.