To comprehend this point, it is useful to decompose long-term nominal yields into four components: expected inflation over the term of the asset; the expected path of short-term real rates; the inflation risk premium and real term premium, which together represent the compensation required by investors for holding long-term bonds as opposed to rolling over short-term securities.
All these components have contributed to the very low long-term rates we observe today. From a long-term perspective, nominal yields on long-term bonds have been on a declining trend in all major advanced economies since the 1980s.