Study notes

The Demographic Transition Model (DTM)

  • Levels: AS, A Level
  • Exam boards: AQA, Edexcel, OCR, IB

The DTM is a model of population change from a low stable population to a high stable population as a result of a preliminary fall in the death rate from a high level (45/1000 p.a. to around 9/1000 p.a.) to be followed later by a fall in the birth rate. The time-lag between the decline in the two measures of natural population change results in a period when there are far fewer people dying than being born, resulting in a phase of rapid population growth.

The model was developed in the mid 20th century based on repeated observation of similar population growth patterns in countries as their economies developed. Originally identifying 4 stages, a 5th stage was added towards the end of the century, and some demographers suggest there may be a 6th stage. As such it is an evolving model of demographic structure.


Death rate:

Is high (mid 40s/1000 p.a.) due to:

  • Poor diet
  • Poor sanitation
  • Inadequate hygiene
  • Lack of medical care

Short life-expectancy

Birth rate:

Is high (mid 40s/1000 p.a.) due to:

  • High infant mortality
  • Lack of contraception
  • Children are economic assets (more=better)
  • Status value of a large family to fathers

Large families are a social norm

Total Population

Total population remains low as births are balanced by deaths so irregular annual 'surpluses' are balanced by irregular annual 'deficits' in years when deaths outnumber births.

STAGE TWO: (Defined when the DR starts to fall)

Death rate:

Begins to fall due to:

  • Improving diet
  • Improving living conditions & sanitation
  • Advances in hygiene
  • Improved medical care

Longer life-expectancy

Birth rate:

Remains high

Total Population

Total population begins to rise as the frequency of years in which births outnumber deaths increases.

(Note: it is NOT due to 'more births' but to 'fewer deaths' with 'consistent births')

STAGE THREE (Defined when the BR starts to fall)

Death rate:

Continues to fall

Birth rate:

Begins to fall due to:

  • More widespread use of reliable contraception
  • Children attend school with associated costs
  • Increasing status and choice of women
  • Increased survival rates of infants

Smaller families become the norm

Total Population

Total population rises at its fastest rate at the start of the stage when the surplus of 'births' over 'deaths' is at its maximum. During this phase the rate of increase slows, though the population continues to increase as birth still outnumber deaths.

STAGE FOUR (Defined when the DR & BR level off)

Death rate:

Levels off around 9/1000 p.a.

Birth rate:

Continues to fall with a strong correlation between improving female education and assertiveness and falling fertility.

Total Population

The rise in population slows and then levels as birth rate falls to match the existing death rate.

STAGE FIVE (Defined when the BR slips below the DR)

Death rate:

Death rate increases due to: An ageing population has a higher death rate than a youthful one due to the larger proportion of elderly people reaching the end of their natural lives. There are more elderly people per thousand reaching their extended life expectancy.

Birth rate:

Continues to fall with more women choosing a child-free or child-limited lifestyle..

Total Population

Total population declines as the death rate of an ageing population rises higher than the still-reducing birth rate.

Is male fertility in crisis?

The Mechanism of the DTM

Early changes in the Death Rate are brought about by economic improvements. The ability to buy more food and with improved nutrition, the ability to pay for better housing, to pay a doctor's fees etc. These are often associated with economic development (the Industrial Revolution in many European countries and North America in the 19th century, or globalisation of manufacturing in many Asian economies in the second half of the 20th century). Changes in the Birth Rate are more often a consequence of social changes and shifts in generational attitude – particularly towards the education of girls, the status of women within a relationship, and attitudes towards the use of reliable contraception. These take longer to permeate a society and explains the time-lag between the fall in the Death Rate and the later decline in the Birth Rate.

The Value of the DTM

The correlation between developing economies and a decline in first the death rate, then the birth rate has been observed in many countries around the world in different stages of development. It is an empirical model – the result of observation and data collection.

It can be used to analyse the reasons behind population change, so national governments can modify the factors to bring about desired impacts. The One-Child Policy of the Chinese government from 1980 can be seen as desire to bring about a Stage 3 and 4 faster than they would otherwise have occurred.

It can be a forecasting model, with demographers anticipating the likely future population projections for countries, regions or globally. This allows governments to plan for anticipated changes in the proportions of young people or elderly populations. The UK government's raising of the age at which the state pension can be accessed is a result of it preparing for an increasingly ageing population with fewer 'economically active' contributors to the revenue base as a proportion of the total population.

Issues with the DTM

While the model can help forecast future population scenarios, it can't be 'predictive' – as each country has individual and unique features that may vary from those encountered by other countries. Almost a quarter Russian men do not survive beyond their mid 50's, in part due to lifestyle choices, despite continuing economic development.

Economic development does not always result in social development that results in rapidly decreasing fertility rates. Some societies maintain traditional views on women, their education, their role, and their status in a marriage so that fertility rates remain higher than may be anticipated.

Death rates in many rural areas of sub-Saharan Africa have remained higher than may have been expected given the economic development of many countries in the region due to the prevalence and impact of HIV/Aids.

Fertility trends appear to continue despite economic development ceasing or even reversing. Japan's economy has stagnated for nearly two decades now and yet it continues to see a slump in its birth rate and the most acute ageing population in the world. Social trends are continuing irrespective of the economic direction, so perhaps the two are not connected as closely as thought.

The original DTM had four stages. This was then expanded to a fifth stage in the latter part of the 20th century. Some demographers are now suggesting a sixth stage. We are still not sure how this model will evolve.

Migration impacts can influence and alter both natural increase/decrease and actual increase/decrease depending on the age, fertility, social attitudes and gender of those arriving as immigrants, and those leaving as emigrants.

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