The Leslie model modified for fertility and immigration: the inefficiency of immigration-based population stabilization

The aim of this chapter is to evaluate and compare the impact that the increase in fertility rates and the use of immigration have on population stabilization. Based on the Leslie population model, the modified approach used in this paper introduces two parameters to manage fertility and immigration.In order to achieve population stabilization, the two parameters are controlled so that the female Leslie matrix truncated by age could have a dominant eigenvalue of 1. We show that the immigration tool is inefficient since it leads to a stabilized population that is too large in size and unbalanced towards its older components. Simulations are provided for the Italian data comparing the demographic dynamics corresponding to different scenarios determined by proper choices of the parameters used to achieve population stabilization.