Population Structure and Migration

This lesson explores how populations are structured by age and sex, the concept of dependency, and the causes, patterns, and consequences of migration. You will study key theoretical frameworks including Ravenstein's Laws of Migration (1885) and Lee's Push-Pull Model (1966), alongside contemporary case studies from the UK and globally.

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Age-Sex Structure

The age-sex structure of a population describes the proportion of people in different age groups, divided by sex. It is typically represented using a population pyramid.

Dependency Ratios

Key Definition: The dependency ratio measures the proportion of the population that is economically dependent (too young or too old to work) relative to the working-age population.

Measure	Formula	Interpretation
Total Dependency Ratio	((0–14 age group + 65+ age group) / 15–64 age group) × 100	Higher values mean more dependants per worker
Youth Dependency Ratio	(0–14 age group / 15–64 age group) × 100	High in Stage 2/3 DTM countries
Old-Age Dependency Ratio	(65+ age group / 15–64 age group) × 100	High in Stage 4/5 DTM countries

UK example (2023 data, ONS):

• Total population: ~67.7 million
• 0–14: 17.6% (youth dependants)
• 15–64: 63.8% (working-age)
• 65+: 18.6% (old-age dependants)
• Total dependency ratio: approximately 57 (i.e., 57 dependants for every 100 workers)

The Ageing Population Challenge

An ageing population occurs when the median age of a population increases, typically because of falling fertility and rising life expectancy. This creates several challenges:

• Increased healthcare costs — older people require more medical care; the NHS spends approximately 2.5 times more per capita on over-65s than on working-age adults
• Pension burden — state pensions must be funded by a shrinking workforce; the UK State Pension age is rising to 67 by 2028 and may reach 68 by the late 2030s
• Labour shortages — fewer workers to fill jobs, particularly in sectors like care, construction, and agriculture
• Housing — demand for sheltered housing and care homes increases
• Changing consumer patterns — reduced demand for school places and children's goods; increased demand for healthcare, leisure, and retirement services

Exam Tip: Ageing is not inherently negative. Older people contribute as consumers, carers (especially grandparents), volunteers, and taxpayers. Avoid the trap of presenting ageing purely as a "problem" — a balanced evaluation will score higher marks.

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Migration: Definitions and Types

Key Definition: Migration is the permanent or semi-permanent movement of people from one place to another. It may be internal (within a country) or international (across borders).

Type	Definition	Example
Immigration	Movement into a country	Polish workers moving to the UK after 2004 EU enlargement
Emigration	Movement out of a country	UK retirees moving to Spain
Net migration	Immigration minus emigration	UK net migration was +685,000 in year ending June 2023 (ONS)
Internal migration	Movement within a country	Rural-to-urban migration in India
Voluntary migration	By choice, typically for economic or lifestyle reasons	Skilled workers moving to the Gulf States
Forced migration	Compelled by war, persecution, or disaster	Syrian refugees fleeing civil war (2011–present)
Temporary/circular migration	Seasonal or fixed-term movement	Mexican agricultural workers in the USA

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Ravenstein's Laws of Migration (1885)

Ernst Georg Ravenstein, a German-English geographer, analysed census data from England and Wales to formulate a set of generalisations about migration patterns. Published in 1885, these remain influential:

1. Most migrants move only a short distance — migration decreases with distance (distance-decay effect)
2. Migration occurs in stages — rural to small town, small town to city, city to metropolis
3. Long-distance migrants tend to move to major centres of commerce and industry
4. Each migration stream produces a counter-stream — e.g., movement from rural to urban areas is partly offset by urban-to-rural movement
5. Urban dwellers are less migratory than rural dwellers
6. Females are more migratory than males over short distances; males dominate long-distance and international migration
7. Migration increases with economic development and improvements in transport

Evaluation of Ravenstein

Strengths:

• One of the first systematic attempts to theorise migration
• Many generalisations remain broadly valid (e.g., distance-decay)
• Influenced subsequent migration theories