Age-Specific Mortality and Fertility Rates for Probabilistic Population Projections

TL;DR

This paper details the methodology behind the UN's 2014 probabilistic population projections, focusing on deriving age-specific mortality and fertility rates, identifying limitations, and proposing improvements, all implemented in the bayesPop R package.

Contribution

It introduces methodological enhancements for deriving age-specific rates in probabilistic population projections, improving accuracy and addressing previous limitations.

Findings

Enhanced methods for age-specific mortality and fertility rate estimation.

Implementation of improvements in the bayesPop R package.

Identification of limitations in previous projection methods.

Abstract

The United Nations released official probabilistic population projections (PPP) for all countries for the first time in July 2014. These were obtained by projecting the period total fertility rate (TFR) and life expectancy at birth ($e_0$) using Bayesian hierarchical models, yielding a large set of future trajectories of TFR and $e_0$ for all countries and future time periods to 2100, sampled from their joint predictive distribution. Each trajectory was then converted to age-specific mortality and fertility rates, and population was projected using the cohort-component method. This yielded a large set of trajectories of future age- and sex-specific population counts and vital rates for all countries. In this paper we describe the methodology used for deriving the age-specific mortality and fertility rates in the 2014 PPP, we identify limitations of these methods, and we propose several methodological improvements to overcome them. The methods presented in this paper are implemented in the publicly available bayesPop R package.