Reconciling forecasts of infant mortality rates at national and sub-national levels: Grouped time-series methods

TL;DR

This paper develops and evaluates grouped time-series methods to reconcile infant mortality rate forecasts at national and sub-national levels, ensuring consistency across hierarchical data for better policy planning.

Contribution

It extends existing grouped time-series forecasting methods by incorporating interval forecast reconciliation via bootstrap, improving accuracy at multiple hierarchical levels.

Findings

Grouped methods improve forecast accuracy over independent models.

Bootstrap-based interval reconciliation enhances prediction reliability.

Methods are effective for demographic rate forecasting in Australia.

Abstract

Mortality rates are often disaggregated by different attributes, such as sex, state, education, religion or ethnicity. Forecasting mortality rates at the national and sub-national levels plays an important role in making social policies associated with the national and sub-national levels. However, base forecasts at the sub-national levels may not add up to the forecasts at the national level. To address this issue, we consider the problem of reconciling mortality rate forecasts from the viewpoint of grouped time-series forecasting methods (Hyndman et al., 2011). A bottom-up method and an optimal combination method are applied to produce point forecasts of infant mortality rates that are aggregated appropriately across the different levels of a hierarchy. We extend these two methods by considering the reconciliation of interval forecasts through a bootstrap procedure. Using the regional infant mortality rates in Australia, we investigate the one-step-ahead to 20-step-ahead point and interval forecast accuracies among the independent and these two grouped time-series forecasting methods. The proposed methods are shown to be useful for reconciling point and interval forecasts of demographic rates at the national and sub-national levels, and would be beneficial for government policy decisions regarding the allocations of current and future resources at both the national and sub-national levels.