Refining seasonal mortality estimates through age adjustment: Evidence from Serbia, 2015–2023

Ivan Marinković

doi:10.4054/DemRes.2026.54.15

Volume 54 - Article 15 | Pages 471–480

Refining seasonal mortality estimates through age adjustment: Evidence from Serbia, 2015–2023

By Ivan Marinković

Date received:

20 Sep 2025

Date published:

10 Mar 2026

Word count:

2288

Keywords:

age adjustment, excess mortality, life expectancy, mortality, mortality estimates, seasonal fluctuations, Serbia

DOI:

10.4054/DemRes.2026.54.15

Supplementary Material:

54-15 supplementary table (pdf file, 141 kB)

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Abstract

Background: Seasonal fluctuations in mortality are a persistent demographic and public health phenomenon. The ideal mortality (IDE) framework estimates seasonal excess mortality by comparing observed outcomes with a counterfactual based on the lowest-mortality seasonal window.

Objective: This study evaluates the validity of the IDE framework when applied to age- and sex-specific mortality in Serbia and proposes an age-structure adjustment (IDEadj) to address anomalies in age-specific estimates.

Methods: Using mortality data for Belgrade and Vojvodina for the period 2015–2023, we construct the IDE baseline based on the three months with the lowest total mortality in each year. Age-specific mortality rates and life expectancy at birth (e₀) are compared across observed, IDE, and IDEadj scenarios.

Results: The IDE framework yields higher life expectancy than observed mortality but produces systematic age-specific inconsistencies. IDE mortality rates occasionally exceed observed values at younger ages and fall to implausibly low levels at older ages, reflecting a mismatch between the age distribution of deaths in the lowest-mortality window and the annual pattern. The IDEadj approach corrects these distortions by aligning age-specific mortality with the observed annual age structure, while preserving the overall magnitude of seasonal gains in life expectancy.

Conclusions: Age-structure adjustment improves the internal consistency and interpretability of seasonal mortality estimates without altering their aggregate magnitude. The IDEadj framework refines the original IDE approach and provides a demographically coherent basis for assessing seasonal mortality effects.

Contribution: By identifying and correcting age-specific artefacts inherent in the IDE framework, this study provides a demographically coherent extension that enhances the analysis of seasonal mortality patterns.

Author’s Affiliation

Ivan Marinković - Institut društvenih nauka, Serbia EMAIL

Refining seasonal mortality estimates through age adjustment: Evidence from Serbia, 2015–2023

Abstract

Author’s Affiliation

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