On a microdemographic framework for decomposing contemporary fertility dynamics

Area of Science:

• Demography
• Sociology
• Public Health

Background:

• The Total Fertility Rate (TFR) is a widely used metric but obscures underlying fertility dynamics.
• Decomposition of TFR into its components can provide a more nuanced understanding of fertility trends.

Purpose of the Study:

• To introduce and validate the Total Maternal Rate (TMR) and Children per Mother (CPM) as independent components of fertility.
• To propose the Microdemographic Framework (MDF) for enhanced demographic analysis and policy evaluation.
• To highlight the limitations of TFR and the benefits of using TMR, CPM, and Total Childlessness Rate (TCR).

Main Methods:

• Analysis of aggregated birth data from over 158 million mothers in Italy, Japan, UK, and US.
• Validation and extension using data from 156 million women across 29 higher-income economies.
• Application of entropy analysis, explanatory power modeling, and wavelet coherence testing.

Main Results:

• TFR results in a 49% information loss compared to decomposed components TMR and CPM.
• TMR and CPM were found to be statistically independent, revealing ambiguity in TFR.
• CPM remained stable, while TMR showed sharp declines, patterns masked by TFR.

Conclusions:

• The Microdemographic Framework (MDF), comprising TMR, CPM, and TCR, offers superior analytical resolution compared to TFR.
• The independence of TMR and CPM provides critical insights for demographic analysis and policy.
• Reporting TMR, CPM, and TCR alongside TFR can facilitate more timely and targeted demographic decision-making, especially in low-fertility settings.