Question: In an article titled "CUNA Mutual Looks for Nonsalable Corporates" that appeared in the November 4, 1991, issue of bond Week , p. 6, Joe Go glia, a portfolio manager for CUNA Mutual Insurance Group, stated that he invests in "planned amortization class tranches, which have less exposure to prepayment risk and are more positively convex than other mortgage-backed." Is this true?