(三) 公債殖利率與生育率之間為正向關係、與人口成長率之間為負向關係，顯示生育率下降將導致未來人口遞減，致使需求不足及產業萎縮，進而影響經濟成長，而且未來人口老化後，其投資組合由高風險股票轉換為較低風險之債券，因此對債券產生超額需求，令公債殖利率下跌。 Many countries throughout the world are experiencing changes in demographics as a result of a low fertility rate. Local and foreign studies currently available all point out that the changes in demographics do affect a nation''s long-term macroeconomics; however, these studies rarely discuss whether a long-term equilibrium exists between demographics (using fertility rate and population growth as variables) and government bond yields.
This paper aimed to investigate how changes in demographics and macroeconomic variables affect government bond yield rates. The empirical research involved the use of panel data across 29 nations, including 28 OECD members plus Taiwan, a fixed effects model, and 7 independent variables to perform a regression analysis on government on yield rates. The results are as follows:
(1) Although there are no significant relationships between government bond yield rates and GDP growth or unemployment rate, it was observed, however, that an increase in the unemployment rate is soon followed by stagnant economic growth and eventually a fall in government bond yields. There is a significant relationship between government bond yields and laborers’ participation in lag intervals. Government bonds yields are positively correlated with the consumer price index, which is consistent with the classical expectation theory.
(2) Government bond yields are positively correlated with the aggregate savings rate, indicating that people tend to save more when doubts accumulate towards economic prospects; after a prolonged period, high savings will drag down economic growth and eventually cause government bond yields to fall.
(3) Government bond yields are positively correlated with fertility rate, and negatively correlated with population growth. This shows that a fall in fertility rate reduces future population growth, creating insufficient demands to support industry growth. In addition, as the general population ages, their investment portfolio will shift from high risk instruments such as equity stocks to lower risk instruments such as bonds; this in turn creates excess demand for bonds and causes government bond yields to fall.