In an intertemporal general equilibrium framework, the economic mechanism of how saving rate and interest rate are affected by shocks of birth or death rates is discussed. Redistributions of consumption within the population is found to be the key driving force, given a small enough elasticity of intertemporal substitution (EIS<1). Quantitatively, an empirical analysis using cross-national panel data indicates that birth and death rates affect the saving rate (or interest rate) through not identical channels. Birth rate affects saving rate positively, whereas death rate affects it negatively, and the effect of birth rate on saving rate is stronger than that of death rate. By contrast, interest rate is decreasing in the birth rate and increasing in the death rate, and the effect of birth rate on interest rate is smaller than that of death rate.