Definitions of net migration, immigration and emigration

Economic Development – Population (IGCSE 0455)

1. Population Change – the Three Components

• Births (natural increase) – measured by the crude birth rate (CBR)
  CBR = (Number of live births ÷ Mid‑year population) × 1 000
• Deaths (natural decrease) – measured by the crude death rate (CDR)
  CDR = (Number of deaths ÷ Mid‑year population) × 1 000
• Migration – movement of people across borders, expressed as net migration.

The overall change in a country’s population in a given period is:

$$\Delta P = (\text{Births} - \text{Deaths}) + \text{Net Migration}$$

Or, using rates (per 1 000):

$$\Delta P = (\text{CBR} - \text{CDR}) + \text{Net Migration (per 1 000)}$$

2. Migration – Key Definitions

Immigration

The movement of people into a country or region with the intention of residing there (temporarily or permanently). Those who move in are immigrants.

Emigration

The movement of people out of a country or region to settle elsewhere (temporarily or permanently). Those who move out are emigrants.

Net Migration

The difference between the number of immigrants and the number of emigrants during a specified period:

$$\text{Net Migration} = \text{Immigrants} - \text{Emigrants}$$

• Positive net migration → population gain.
• Negative net migration → population loss.

3. Why Migration Rates Differ – Push‑ and Pull‑Factors

• Economic factors: higher wages, better job prospects (pull); unemployment or low wages (push).
• Political & security factors: war, persecution, political instability (push); political stability, safety (pull).
• Social & cultural factors: family reunification, education, lifestyle preferences (pull); lack of services, discrimination (push).
• Environmental factors: natural disasters, climate change, resource scarcity (push); favourable climate, safe environment (pull).
• Policy factors: visa regulations, refugee programmes, immigration quotas (pull); restrictive policies, border controls (push).

4. Why Birth and Death Rates Differ

• Fertility determinants (affecting CBR)
  • Economic development – higher income usually lowers fertility.
  • Education, especially of women.
  • Access to contraception and family‑planning services.
  • Cultural or religious norms regarding family size.
  • Urbanisation – city living often reduces desired family size.
• Mortality determinants (affecting CDR)
  • Healthcare quality and availability.
  • Nutrition and food security.
  • Sanitation and clean water.
  • Prevalence of disease, vaccination programmes.
  • Age structure – older populations have higher death rates.

5. Numerical Example & Practice

Example: In 2023, Country X recorded 120 000 immigrants and 80 000 emigrants.

Net migration = 120 000 – 80 000 = +40 000 (a net gain).

Practice Questions

1. Country Y has 95 000 immigrants and 110 000 emigrants in one year. Calculate net migration.
2. If the same country also had 1 200 000 births and 950 000 deaths, what is the total population change for the year? (Use the formula in section 1.)

6. Population Structure

• Age‑sex distribution – shows the number of males and females in each age group.
• Population pyramid – graphical representation of the age‑sex structure.
  • Wide base → high birth‑rate, young population.
  • Narrow base → low birth‑rate, ageing population.
  • Bulging middle → large working‑age cohort (potential “demographic dividend”).

How to Interpret a Pyramid

1. Identify the shape of the base and the top.
2. Link a wide base to high fertility and a high dependency ratio (many children to support).
3. Link a narrow base and wide top to an ageing population and possible labour shortages.
4. Discuss implications for schools, health services, housing and the labour market.

7. Optimum Population

The optimum population is the size at which a country can provide a satisfactory standard of living for its citizens, given the available resources, technology and environment. It is a balance between:

• Resource availability (food, water, energy, land).
• Employment opportunities and income levels.
• Environmental sustainability.

Too low a population may lead to under‑utilised resources and labour shortages; too high a population can cause unemployment, pressure on housing, health services and the environment.

8. Effects of Changes in Population Size & Structure

• Housing & infrastructure: Rapid growth raises demand for new homes, roads, water and electricity.
• Education & health: More children → greater need for schools, teachers, hospitals and doctors.
• Labour market
  • Growth can expand the labour force, creating a “demographic dividend” if jobs are created.
  • If job creation lags, unemployment and under‑employment rise.
• Living standards
  • Positive impact when economic growth keeps pace with population growth.
  • Negative impact when resources become scarce, lowering per‑capita income.
• Environment: More people increase pressure on natural resources, waste generation and greenhouse‑gas emissions, affecting sustainability.
• Ageing populations: Higher proportion of elderly raises health‑care costs and may require policy changes (pensions, retirement age).
• Young, rapidly growing populations: Need for large investments in education and job creation to avoid future unemployment.

9. Summary Table – Key Population Indicators