Explaining a population pyramid anomaly
A country of 28 million people has a population pyramid showing an unusually narrow cohort at ages 20–29 and a bulge at ages 45–54, with a smaller secondary bulge at ages 10–19. Total fertility rate fell from 4.1 in 1990 to 1.7 in 2023. Net migration was strongly negative from 2005 to 2015 (averaging −180,000 per year) and has been slightly positive since 2018. Life expectancy is 79 years. Youth unemployment is 24%, and 38% of the population is under 25. A student claims the narrow 20–29 cohort is 'simply because people are having fewer babies'.
1. Evaluate the student's explanation and propose the most likely causes of the narrow 20–29 cohort and the 45–54 bulge.
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The student's explanation is inadequate. Falling fertility affects the base of the pyramid (ages 0–19), not a cohort already born 20–29 years ago. A narrow band at 20–29 must be explained by events affecting that cohort after birth: out-migration, mortality, or a birth dearth when they were born.
Most likely causes of the narrow 20–29 cohort:
- Age-selective out-migration. Net migration averaged −180,000/yr from 2005–2015. Migrants are typically young adults, so this period maps directly onto today's 20–29 band. This is the strongest explanation.
- Youth unemployment (24%) provides a push factor, reinforcing emigration of young adults.
- Possibly a birth decline around 1995–2005, but the data do not show a fertility collapse then; fertility was still falling from 4.1 in 1990, so a modest birth decline may contribute but is unlikely to be the main cause.
The 45–54 bulge corresponds to a birth surge around 1970–1980, when fertility was high (well above 4.1 before 1990). It reflects past high fertility now ageing through the pyramid, not recent change.
The secondary 10–19 bulge is harder to explain and may reflect a temporary fertility uptick or improved child survival; it should be flagged as uncertain without birth-year data.
2. Explain the likely future implications of this age structure for the country's economy and services over the next 20 years.
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1. Labour force squeeze and dependency shift. The narrow 20–29 cohort will move into prime working ages over the next decade, meaning a smaller workforce relative to the large 45–54 cohort approaching retirement. The old-age dependency ratio will rise as the bulge retires, increasing pressure on pensions and health care.
2. Youth unemployment and skills mismatch. With 24% youth unemployment and 38% under 25, the country faces a paradox: a large youth population but limited absorption into jobs. If out-migration continues, this represents a loss of human capital ('brain drain') that further shrinks the future workforce.
3. Education demand. The 10–19 bulge will require secondary and tertiary capacity now, but demand will fall sharply once that cohort passes through, creating a risk of over-built infrastructure. Planning should anticipate the decline.
4. Health and aged care. As the 45–54 bulge ages, demand for aged care and chronic disease services will rise steeply within 20 years, while the smaller younger cohorts provide a narrower tax base to fund it.
5. Migration policy tension. Slightly positive net migration since 2018 may partially offset workforce losses, but if it is not age-targeted it may not fill the gap left by the missing 20–29 cohort.
Overall: the country faces a demographic 'waist' - a missing generation of workers - that will constrain growth and strain services unless productivity, participation or migration policy responds.