The University of California system's retirement fund faces a shortfall of $20 billion, according to a study released Monday, the Los Angeles Times reported. A committee that produced the study offered a number of recommendations for closing the gap, including raising the retirement age for new employees, increasing the contributions made by both the university and its employees, and reducing benefits. Faculty members worry that some of the changes could make employment at the university less attractive for some of the academic talent they would like to recruit. Mark G. Yudof, the system president, recently sent a letter to all employees in which he said some changes are essential. "If we do nothing, in four years, the university will be spending more on retirement programs each year than we do on classroom instruction," he said.