A new parametric model for fitting fertility curves

Abstract

What is the optimum way of describing the age-specific fertility pattern by mathematical functions? We propose a parametric fitting model, based on a mixture of Weibull functions, which performs well for countries where the fertility curve shows a non-traditional pattern. We also consider a simplified version of this model with a reduced number of parameters that can be applied to fit fertility curves in countries where the fertility pattern exhibits a classical shape. To test the new model, fertility curves for a range of countries and years are fitted empirically. The results show that both versions of the new model outperform existing procedures in most cases.

Keywords:

• fertility curve
• Weibull function
• age-specific fertility rates

Notes

1. S. Bermúdez, J. A. Hernández, and J. Planelles are at Instituto de Estadistica de Andalucía, Sevilla, Spain. S. Bermúdez is also at Universidad Pablo de Olavide, Sevilla, Spain. R. Blanquero (corresponding author) is at Universidad de Sevilla, Departamento de Estadística e Investigación Operativa, Facultad de Matemáticas, Campus de Reina Mercedes, 41012 Sevilla, Spain. E-mail: [email protected]

2. This work has been partially supported by projects MTM2009-14039 of MCI, TIC-6064 and FQM-329 of Junta de Andalucía, Spain.