Historical Development of Demographic Transition Theory
The Demographic Transition Theory (DTT) is a model that describes how birth and death rates change over time in a population. Over several decades, researchers attempted to understand and explain population dynamics.
The first phase of DTT began in the mid-18th century with Thomas Malthus’ work, who believed that population growth would inevitably outstrip food supply, causing social and economic problems. Malthus’ work influenced the development of early population growth theories, but others later challenged his pessimistic predictions. (See: Malthusian Theory of Population)
Demographers began to study population growth more thoroughly in the early twentieth century. Warren Thompson proposed the concept of a “demographic transition” in 1929, in which birth and death rates decrease as a society progresses from pre-industrial to industrialized conditions.
Scholars expanded on Thompson’s work and developed the DTT model into a more complex and nuanced theory during the 1940s and 1950s. Frank Notestein expanded the model to include four stages of demographic transition. He proposed the concept of a “population explosion” caused by a decrease in death rates without a corresponding decrease in birth rates.
Read: Sustainable Population Growth Theory
Population explosion refers to a sudden and rapid increase in the size of a population over a relatively short period. In the context of demographic transition theory, population explosion can occur during the second stage of the model, when there is a sharp decline in the crude death rates, but the crude birth rates remain high. This leads to a period of rapid population growth and an overall increase in the population size.
The population explosion is often associated with developing countries with inadequate healthcare and family planning services. This can lead to high fertility rates and many children per woman, contributing to the population explosion.
Researchers began investigating the social and economic factors influencing demographic change in the 1960s and 1970s. They discovered that urbanization, increased access to healthcare and education, and shifts in cultural attitudes toward family size can all significantly impact birth and death rates.
Demographic Transition Theory of Population Explained
The main concept of Demographic Transition Theory of Population is the transformation of population dynamics that occur in a society over time as economic and social changes occur. According to the theory, populations transition from high to low birth and death rates due to economic development and public health and education improvements.
This transition is typically divided into three stages: the pre-industrial, transitional, and industrial. Both birth and death rates are high in the pre-industrial stage, resulting in slow population growth. Death rates fall during the transitional period as healthcare and sanitation improve, but birth rates remain high, resulting in rapid population growth.
Finally, as education and contraception access improve, birth and death rates fall in the industrial stage, resulting in slower population growth. According to the theory, these changes significantly impact a society’s economy, social structure, and environment.
Assumptions of demographic transition theory
The demographic transition theory is based on certain assumptions, which include:
- All societies follow a similar pattern of demographic transition.
- Fertility and mortality rates are the main determinants of population growth.
- The changes in fertility and mortality rates are caused by social and economic development.
- Urbanization, industrialization, and education are the major factors responsible for the decline in fertility rates.
- The decline in mortality rates is due to improvements in public health, medical science and technology.
- The demographic transition is a gradual and natural process as a society develops.
- The demographic transition theory assumes that government policies have no significant impact on fertility and mortality rates.
The Four Stages of Demographic Transition Theory of Population
The demographic transition theory describes how countries transition from traditional to modern industrialized societies in terms of population growth. The theory divides the world into four stages, each marked by distinct birth rate changes, death rate, and population growth.
Stage I (Pre-Industrial Stage): Societies in the first stage have high birth and death rates, resulting in a relatively slow population growth rate. This stage is typical of pre-industrial societies, with high levels of disease, poor living conditions, and limited access to medical care.
Stage II (Urbanizing Stage): In the second stage, societies see rapid declines in death rates while birth rates remain high, resulting in rapid population growth. This stage is distinguished by advances in medical care, public health measures, and living standards, which result in lower mortality rates.
Stage III (Mature Industrial Stage): In the third stage, societies experience a decrease in birth rates while maintaining low death rates, resulting in a slower population growth rate. This stage is distinguished by increased access to family planning, education, and economic opportunities, all contributing to decreased fertility rates.
Stage IV (Post Industrial Stage): Societies in the fourth and final stage have low birth and death rates, resulting in a stationary population at a low level. This stage is typical of modern, industrialized societies, where women have greater access to education and employment opportunities, and family planning is widely available.
The following diagram can help to explain these stages of demographic transition:
The graph above depicts how a country’s population evolves as it grows economically. The population grows slowly in Stage I due to high birth and death rates. The population explodes in Stage II as the birth rate remains high, but the death rate rapidly declines. The birth rate begins to fall in Stage III, resulting in a slower but growing population. Finally, Stage IV’s birth and death rates are low, resulting in a low-level stable population. By going through these stages of demographic transition, a country can go from being poor with high birth and death rates to being wealthy with low birth and death rates.
Mathematical/ Econometric representation of the Demographic Transition Model
Various mathematical/econometric models, such as the logistic, Lotka-Volterra, and Leslie matrix models, can represent the demographic transition model.
The logistic model is a popular mathematical model that assumes population growth is proportional to population size and carrying capacity of the environment. This model can be expressed as follows:
dP/dt = rP(1 – P/K)
Where:
dP/dt: rate of change in population size over time
r: growth rate of the population
P: population size
K: carrying capacity of the environment
The Lotka-Volterra model is another option based on the predator-prey relationship between birth and death rates. This model can be expressed as follows:
dN/dt = rN – bNP
dP/dt = cbNP – dP
Where:
dN/dt: rate of change in the population of the prey (humans)
dP/dt: rate of change in the population of the predator (disease)
r: growth rate of the prey
b: rate at which the predator kills the prey
c: rate at which the predator infects the prey
d: death rate of the predator
Finally, the Leslie matrix model is a more complex and considers the population’s age structure. It can be stated as follows:
N(t+1) = AN(t)
Where:
N(t+1): population at time t+1
N(t): population at time t
A: the Leslie matrix, which describes the transition of individuals from one age group to another
Criticisms of Demographic Transition theory
Some major criticisms of the demographic transition theory are explained as follows:
- Cultural and social factors: According to the demographic transition theory, changes in fertility and mortality rates are primarily influenced by economic factors. Religious beliefs, gender roles, and family values, on the other hand, may play a significant role in shaping population dynamics.
- Oversimplification: The demographic transition theory offers a simplified model of demographic change that may not apply to all countries or regions. Different patterns of fertility and mortality change may occur in different countries, while others may skip certain stages entirely.
- Lack of policy guidance: The demographic transition theory does not provide clear guidance for governments and policymakers on responding to changing population dynamics. Policies aimed at lowering fertility rates, such as family planning programs, may sometimes be effective. Policies that address economic and social factors may be more appropriate in other cases.
- Environmental sustainability: The demographic transition theory is primarily concerned with population growth and economic development, but it may overlook the significance of environmental sustainability. Population growth may strain natural resources and ecosystems, resulting in environmental degradation and other negative consequences.
- The European Experience, not a Theory: One criticism leveled at the demographic transition theory is that it is based on European experience and thus cannot be applied to other parts of the world without modification. To explain the demographic changes that occurred in Europe during the 18th and 19th centuries, the demographic transition theory was developed. According to critics, the theory fails to account for the unique historical, cultural, and economic factors that influence population dynamics in other parts of the world.Some critics argue that the theory cannot be applied to developing countries, where high birth rates are frequently attributed to cultural or religious beliefs rather than economic factors. Large families are seen as a source of pride and security in some parts of the world, and children are valued as a source of labor or support for aging parents. Poverty, a lack of access to education and healthcare, and political unrest can all contribute to high birth rates in developing countries.Furthermore, critics argue that the demographic transition theory is based on a limited understanding of population dynamics that fails to account for modern society’s complexities. The theory assumes that economic development will inevitably lead to a decrease in birth rates, but in practice, this has not always been the case. Despite high levels of economic development, birth rates in some developed countries have remained stable or even increased.
Conclusion
Warren Thompson proposed the demographic transition Theory in 1929, with four stages: pre-industrial, urbanizing/industrializing, mature industrial, and post-industrial. According to the model, economic development can reduce crude death rates, and access to healthcare, sanitation, and information can improve human health.
The model also includes a behavioral component, in which people alter their decisions when they access information or opportunities that reduce certain behaviors. Fertility rates are used to evaluate the link between economic development and population growth. The clear associations between economic development and fertility rate prove that the model effectively understands these relationships.