3 / 13  BIS central bankers' speeches  4 / 13  BIS central bankers' speeches  Source: Eser, Lemke, Nyholm, Radde, and Vladu (mimeo).7 Downward pressure on yields is expected to be very persistent and to decline only gradually, but consistently, as we move forward in time, because of what is referred to as the “portfolio ageing” effect.
The effects of our purchases of long-dated assets on market yields are principally due to the fact that we withdraw duration from private hands, and as the securities we hold in our portfolio draw closer to maturity and “lose duration” progressively, the overall amount of duration contained in our portfolio has a tendency to melt away.