At the height of the property bubble, California's giant pension fund, Calpers, made a fateful decision: It aggressively poured money into real estate. As a result, today it's one of the biggest owners of undeveloped residential land in America. Partly because of these investments, California Public Employees' Retirement System is struggling to avoid one of its worst annual declines since its 1932 inception. Calpers has lost almost a quarter of its assets since July 1, the start of the current fiscal year. The problems come at a time of uncertainty for the nation's largest public pension fund, which has been...