The demographic transition model (DTM) and its stages

The demographic transition model (DTM) is a framework that illustrates how birth rates and death rates change over time as a country develops economically. It outlines five distinct stages, each reflecting different population growth patterns based on these rates.

Stages of the demographic transition model

• Stage 1 - High and variable - Both birth rates and death rates are high and fluctuate, leading to unstable population growth. No countries are currently at this stage, though some indigenous tribes remain here. Historically, the UK was in this stage until around 1750.
• Stage 2 - Early expanding - Birth rates stay high, but death rates decrease sharply due to improvements in living conditions, resulting in rapid population growth. Countries like Afghanistan, Sudan, and Libya are examples today. The UK moved past this stage by 1850.
• Stage 3 - Late expanding - Birth rates begin to fall while death rates remain low, slowing population growth but still showing an increase. Nations such as Brazil and Argentina are at this stage. The UK reached this point around 1950.
• Stage 4 - Low and variable - Both birth rates and death rates are low and fluctuate, leading to minimal population growth or stability. Most developed countries, including the UK, are currently here.
• Stage 5 - Low declining - Birth rates drop below death rates, causing a population decline. Japan is an example of a country in this stage, reflecting an ageing population.

Key trends in the DTM

• Death rates fall first - Improvements in healthcare and sanitation typically reduce death rates before birth rates decline.
• Population growth pattern - Total population increases significantly during Stages 2 and 3 before stabilising or declining in later stages.
• Economic development link - The model correlates with a country's level of economic progress, moving from low to high development across the stages.

Factors influencing high and low birth and death rates

Birth and death rates are influenced by social, economic, and environmental factors that vary across the stages of the DTM.

High birth rates in early stages (Stages 1 and 2)

Families have many children for several reasons:

• To provide labour for farming or other work.
• To ensure care in old age, as there are no government support systems.
• To maintain family lineage or social status.
• To replace children lost to high infant mortality.

High death rates in early stages (Stage 1)

Mortality is elevated due to:

• Limited access to clean water.
• Insufficient food supplies.
• Poor hygiene and sanitation practices.
• Overcrowded living conditions.
• Spread of contagious diseases.
• Widespread poverty limiting healthcare access.

Low birth rates in later stages (Stages 4 and 5)

Fewer children are born due to:

• High costs of raising children.
• Government support through pensions and health services reducing the need for children as security.
• Increasing numbers of women prioritising careers over large families.
• Greater access to family planning methods.
• Lower infant mortality rates reducing the need for replacement children.

Low death rates in later stages (Stages 3 to 5)

Mortality decreases because of:

• Availability of clean water.
• Consistent and reliable food supplies.
• Improved hygiene and sanitation standards.
• Reduced population density lowering disease spread.
• Advances in vaccinations and medical care.
• Higher overall living standards.

Population pyramids and their relation to DTM stages

Population pyramids are graphical representations of a population's age and sex structure at a given time. They correspond closely with the stages of the DTM, visually depicting shifts in population composition as countries develop.

Characteristics of population pyramids by DTM stage

These shapes reflect the changing dynamics of birth and death rates, with a wide base indicating high fertility and a narrow top showing high mortality in early stages, transitioning to a more balanced or top-heavy structure in later stages.

Alternative demographic transitions and exceptions to the model

While the DTM provides a general framework, it is based on historical data from specific countries like England, Wales, and Sweden. Not all countries follow this exact pattern due to unique historical, cultural, or economic factors, leading to alternative demographic transitions.

Limitations of the standard DTM

• Limited data foundation - The model relies on trends from just a few countries, which may not apply universally.
• Timescale variations - The transition often takes longer in the original countries studied compared to many low-income countries (LICs) today, where changes can occur more rapidly due to modern interventions.
• Diverse patterns - Some nations experience demographic changes that deviate from the standard model due to specific events or policies.

Case of Ireland's demographic transition

• Post-famine dynamics - Following the famine of 1845–1849, Ireland experienced a unique demographic pattern with falling birth rates and rising death rates, contrary to the standard DTM.
• Impact of emigration - Large-scale emigration after the famine contributed to a natural decrease in population, as more people left the country than were born or died within it.
• Deviation from norm - This shows that catastrophic events or social movements can create demographic trends outside the typical progression of the DTM stages.