In a stable population where birth rate equals death rate and both are constant over time, what characterises the age distribution?

• A Progressive narrowing of all age groups — inverted pyramid
• B Expanding base — pyramidal structure with dominant young age groups
• C A stationary population with a fixed age distribution (neither young nor ageing predominance) ✓
• D Selective depletion of the working-age group

Explanation

A stationary population is one where birth rate = death rate (NRR = 1, zero growth), resulting in a stable, unchanging age structure. The age pyramid is neither expanding (pyramidal) nor contracting (inverted). In an expanding population, CBR > CDR, yielding a broad-based pyramid. In a contracting (declining) population, CBR < CDR, yielding an inverted or 'beehive' pyramid. A 'stable population' in demography specifically refers to constant age-specific rates but may still grow if growth rate ≠ 0.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

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