Kenneth L. Trefftzs, 89, economist at the USC Marshall School of Business. Born in Sparta, Ill., he earned bachelor's, master's and doctoral degrees at the University of Illinois and taught two years at what is now Carnegie-Mellon University before joining the USC faculty in 1941. Trefftzs headed the finance department and the board of the USC Faculty Center Assn., helped establish the Troydale faculty housing development and campaigned to establish Coliseum Street School near the campus. He earned awards for excellence in teaching and in 1988 was named distinguished professor emeritus. Former student Karl McMillen funded the Kenneth L. Trefftzs Chair in Finance in his honor. Trefftzs was president of the Western Economics Assn. in 1955-56 and founding president of the Western Finance Assn. a decade later. On April 10 in San Diego.