population growth and structure: measurement and causes of changes in birth rate, death rate, infant mortality and net migration

📈 Characteristics of Countries at Different Levels of Development

Population Growth & Structure

Population growth rate is the percentage change in a country’s population over a year.


Formula: Growth Rate = [(Populationt – Populationt‑1)/Populationt‑1] × 100

Think of it as a garden: if you plant 100 seeds (population) and 5 new seeds sprout each year (births) while 2 seeds die, the garden grows by 3%.

Birth Rate & Causes of Change

  • Higher in low‑income countries due to limited access to contraception and higher child mortality.
  • Lower in high‑income countries because families often choose fewer children and have better access to family‑planning services.
  • Government policies (e.g., China’s one‑child policy) can drastically reduce birth rates.
  • Social changes: urbanisation, education, especially women’s education, shift family size preferences.

Death Rate & Causes of Change

  • Higher in low‑income countries due to infectious diseases, malnutrition, and limited healthcare.
  • Lower in high‑income countries because of advanced medical technology and better living conditions.
  • Infant mortality (death before age 1) is a key indicator of overall health and is usually highest in developing nations.
  • Improved sanitation, vaccination programmes, and clean water reduce death rates over time.

Infant Mortality

Infant mortality rate (IMR) = (Number of infant deaths / Live births) × 1,000

CountryIMR (per 1,000 live births)
Nigeria73
Japan2

Net Migration

Net migration = Immigrants – Emigrants

Countries with high economic opportunities (e.g., USA, Germany) attract many immigrants, leading to a positive net migration. Conversely, countries facing conflict or economic hardship may experience negative net migration.

✏️ Examination Tips

  • Remember the demographic transition model: as a country develops, birth and death rates fall, leading to slower population growth.
  • Use the population pyramid to visualise age structure: wide base = high birth rate, tall top = high life expectancy.
  • When answering “What causes changes in birth rate?” list access to contraception, women’s education, urbanisation, and cultural norms.
  • For “Explain the impact of infant mortality on population growth,” note that high infant mortality reduces the number of children who survive to adulthood, slowing growth.
  • Practice converting raw numbers into rates (e.g., (5,000 births / 100,000 population) × 1,000 = 50 ‰).

Analogies & Examples

  • Population as a river: Births add water, deaths subtract water. Net migration is like water flowing in or out of the river.
  • Infant mortality as a filter: A high filter (high infant mortality) removes many young “particles” before they can contribute to the population.
  • Economic development as a garden’s fertilizer: Fertilizer (better healthcare, education) reduces the “weeds” (high death rates) and encourages healthy growth (lower birth rates).