Change of Age-Specific Fertility Curves in Peninsular Malaysia: An Approach of Functional Data Analysis

Abstract

The fertility pattern has been investigated in several studies but concisely focuses more on discrete data. Thus, this study examines the functional form of fertility changes and identifies the characteristics curve patterns based on mothers’ age group. A set of age-specific fertility rates from year 1968 to 2005 (38 years) is applied in this study. Initially, the observed data will be transformed to logarithm form, then followed by the nonparametric smoothing process using weighted median B-spline which has determined to diminish the observational error and resulting more reliable outcomes. Decomposition procedure by means of functional principal component was carried out to model the fitting curves by expanding the orthonormal basis functions. In particular, the fitted curve components consist of age group mothers. The corresponding results indicated the emergence of continuous decline on fertility curves over the years and mothers towards ages 20s and 40s mainly contributed to the large variability on fertility changes.