Age Structure and Growth in a Rapidly Urbanizing Region
A country of 30 million people has a total fertility rate of 4.2 and a median age of 19. Its age structure shows 45% of the population under 15. Contraceptive prevalence is 30%, and female literacy in rural areas is 55% versus 92% in cities. The government projects that even if fertility falls immediately to replacement (2.1), the population will still reach about 45 million before stabilizing. Urban water demand is rising 5% per year, and the capital already draws groundwater 30% faster than recharge.
1. Explain why the population is projected to keep growing even if fertility drops to replacement, and what this means for planning.
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This is population momentum. With 45% of people under 15 and a median age of 19, a large cohort is entering reproductive age. Even at 2.1 children per woman, the number of births stays high because the number of women of childbearing age keeps increasing for decades. The projection to ~45 million is consistent with momentum, not with continued high fertility. Planning implication: infrastructure must be sized for the committed growth, and demand management is essential because water supply cannot be expanded fast enough. The judgment call: policies that reduce fertility now still help, but they do not avert near-term growth, so water planning must assume the 45 million figure.
2. Which interventions would most efficiently lower fertility, and how would they interact with the water crisis?
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Female education and contraceptive access are the strongest levers. Rural female literacy (55%) lags urban (92%), and contraceptive prevalence is only 30%, so expanding rural schooling and family planning has the highest marginal effect. These are also relatively low-cost and rights-based. Interaction with water: lower fertility reduces long-run demand and buys time, but momentum means near-term demand keeps rising, so supply-side measures (recharge, efficiency, leak reduction, reuse) are still required. The judgment call: invest in education and family planning for the long run while treating water efficiency and recharge as non-negotiable in the short run.