Age Structure

When people live longer and mortality at older ages declines, more individuals survive into advanced age. If birth rates remain low, each new young cohort is smaller than earlier generations. The population pyramid therefore changes from a broad-based shape toward a more rectangular or top-heavy shape, with relatively wider upper age groups. This indicates population ageing rather than rapid youthful growth.

Option A is correct because the upper age groups gain relative weight. A low birth rate does not rapidly widen the base; it tends to keep the base narrow. Older people do not disappear, and all age groups do not decline equally because survival improvements affect older ages particularly. The exact shape depends on migration and other demographic conditions.

The ageing index compares the size of the older population with the size of the child population. It is usually expressed as the number of elderly persons per 100 children. Here the elderly share is 16 percent and the 0–14 share is 20 percent. The percentages can be used as the two population groups: \(16/20\) multiplied by 100 equals 80. Thus, there are 80 persons aged 60 or above for every 100 children aged 0–14.

Choice A is correct. The calculation does not require the total population because the same total is present in both percentages and cancels in the ratio. Choice B, 36, incorrectly subtracts the percentages; choice C reverses the comparison and gives 125, while choice D uses only the elderly percentage. The index is a ratio, not a percentage-point difference, so 80 is the appropriate result.

Migration changes the age distribution when migrants are concentrated in particular age groups. For example, young adults moving for education or work can increase the working-age share in the destination and reduce it in the place they leave, even without an immediate change in births. If migrants have the same age distribution as residents, the overall proportions are less likely to change. Option A is correct.

This pattern is called population momentum. If earlier high fertility produced large young cohorts, many people may enter reproductive ages at around the same time. Even at replacement-level fertility, the large number of potential parents can result in more births than deaths for a period, so population growth may continue. Option A identifies the age-structure feature behind this momentum.

Over the next 5–10 years, this cohort will move through secondary-school ages and toward further education, skills training, and, for some, entry into employment. Planning for these needs can help prevent overcrowding and prepare young people for work. Option A is therefore the most direct priority linked to the cohort's next stages.

Age heaping occurs when reported ages cluster at preferred rounded numbers, often ages ending in 0 or 5. This can create artificial peaks in the age data and distort age-structure analysis. Thus, unusually frequent reporting of ages such as 30, 35, and 40 is called age heaping.

A lower dependency ratio means that, on average, fewer children and older dependents must be supported by each working-age adult. If income does not fall, households may have more money left after meeting essential dependent-related costs such as care, schooling, and daily support. Some of that remaining income can be saved or invested. This is a potential effect, not a guarantee: saving also depends on wages, prices, debt, access to banks, social expectations, and confidence about the future.

Choice A is correct because it explains the income mechanism without claiming that all available money will be saved. Choice B is false because older people do not always save all income. Choice C ignores the real costs of raising and educating children. Choice D is also false because working-age people continue to consume. A lower dependency burden creates an opportunity for higher saving, but good employment and policies are needed to realise it.

Equal total population does not imply equal health needs. A region with many children may require more vaccination, nutrition, pediatric, and maternal-health services. An elderly-heavy region is more likely to need chronic-disease management, rehabilitation, geriatric care, and long-term support. Age structure therefore affects both the type and volume of health resources required. Planning only from total population size can misallocate services because equally large populations may have very different age-specific health demands.

Age structure shows how many children, working-age adults, and older people are in a population. Each group creates different demands on public budgets. More children may require schools, teachers, nutrition programmes, and vaccination. A large working-age group may need skill training, transport, and employment support, while an older population may require hospitals, long-term care, and pensions. Knowing these proportions helps governments plan services and allocate funds instead of relying only on total population.

Option A is correct because it connects age groups with their distinct public needs. B is wrong because needs are not identical across ages. C treats an important planning tool as a mere formality, and D is insufficient because total population does not reveal the age composition. Therefore age-structure analysis makes budgeting more targeted and realistic, so A is the correct choice.

Population ageing is a structural demographic change in which older age groups account for a rising share of the total population over time. It can result from lower fertility, longer life expectancy, and the ageing of large cohorts. It is not merely the normal biological ageing of individuals, because demography examines changes in population proportions. A population may grow while remaining youthful or decline while becoming older. Therefore, ageing means a relative shift in age composition, not simply an increase in total numbers.

A youthful age structure contains a large share of children and adolescents. As these cohorts grow older, many will enter reproductive ages, so the number of people capable of having children can become large. Even if each person has fewer children than earlier generations, the total number of births may remain relatively high because the potential parent population is large. This creates population momentum, although its strength is also affected by mortality, migration, marriage patterns, and future fertility choices.

Choice A is correct because it identifies the main demographic mechanism: many young people will later enter reproductive ages. Choice B is biologically and demographically incorrect. Choice C is an absolute claim; a youthful structure does not mean mortality is zero. Choice D is also false because population size can change through births, deaths, and migration. Thus, youthful age composition creates growth potential, not an unavoidable guarantee of rapid growth.

Persistently small birth cohorts eventually become small working-age cohorts. If more people retire than enter the labour force, labour supply may slow or decline. This can produce worker shortages in some sectors, wage pressure, and rising old-age dependency. Youth dependency may actually fall in such a situation rather than rise. The economic effect of low fertility is delayed: it becomes visible as smaller cohorts age into the labour market while older cohorts move into retirement. Thus, option A follows from cohort replacement over time.

The potential support ratio indicates how many working-age people are available relative to dependents, often especially elderly dependents. A higher ratio suggests a larger potential support base, while a lower ratio may mean a heavier elderly or dependent burden per working-age person. It is not a complete measure of actual economic support because not all working-age people are employed and some older people continue working. Even so, it is useful for assessing the support implications of age structure and the pressure placed on workers by dependent groups.