Demographic Sustainability Level: A Three-Constraint Framework for Minimum Viable Fertility

Abstract

This paper defines the demographic sustainability level (DSL) as the minimum total fertility rate (TFR) that simultaneously satisfies three structural constraints: net reproduction rate (NRR ≥ 1), old-age dependency ratio (OADR ≤ critical threshold), and population decline rate (≤ acceptable bound). We derive a closed-form solution showing that for Turkey’s current mortality and migration parameters, the DSL lies at approximately TFR = 1.84, with a behavioral floor defined by PPR₁ ≥ 0.70.

Key Results

The three-constraint framework yields a coefficient k = 0.478 linking NRR requirements to TFR targets under observed sex ratios and survival probabilities.

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📄 Full paper (PDF) · 📊 R code (sustainability_calculations.R)

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Correspondence: mehmet.sezgin@aile.gov.tr