theories of population

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Theories of Population:

Theories of Population

Demographic Transition Theory:

Demographic Transition Theory The pocess by which fertility rates eventually decline to replacement levels. It attempts to explain why all contemporary developed nations have more or less passed through the same three stages of modern population history. Is a georaphic model used to explain the process of change fom high birth rates and high death rates to low birth rates and low death rates as part of economic development of a country from a pre-industirial to a industilized economy.

Stage 1. High Fluctuating:

Stage 1. High Fluctuating Pre-industrial Society High death rates and birth rates = balance Stage Birth Rate and Death rate are both high. Population growth is slow and fluctuating.


Reasons: Birth Rate is high as a result of: Lack of family planning High Infant Mortality Rate: putting babies in the 'bank' Need for workers in agriculture Religious beliefs Children as economic assets

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Death Rate is high because of: High levels of disease Famine Lack of clean water and sanitation Lack of health care War Competition for food from predators such as rats Lack of education Typical of Britain in the 18th century and the Least Economically Developed Countries (LEDC's) today.

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Demographic Transition Theory

Stage 2 - Early Expanding:

Stage 2 - Early Expanding Developing Country Death rates drop due to technology (improved food supply, health care and education) High birth rates remain = large rise in the population Birth Rate remains high. Death Rate is falling. Population begins to rise steadily.


Reasons: Death Rate is falling as a result of: Improved health care (e.g. Smallpox Vaccine) Improved Hygiene (Water for drinking boiled) Improved sanitation Improved food production and storage Improved transport for food Decreased Infant Mortality Rates Typical of Britain in 19th century; Bangladesh; Nigeria

Demographic Transition Theory:

Demographic Transition Theory

Stage 3 - Late Expanding:

Stage 3 - Late Expanding Birth Rate starts to fall. Death Rate continues to fall. Population rising. Developed Countries Birth rates fall due to access to contraception; increases in wages, the status and education of women; and a reduction in the value of children's work Population growth begins to level off.


Reasons: Family planning available Lower Infant Mortality Rate Increased mechanization reduces need for workers Increased standard of living Changing status of women Typical of Britain in late 19th and early 20th century; China; Brazil

Stage 4 - Low Fluctuating:

Stage 4 - Low Fluctuating Birth Rate and Death Rate both low. Population steady. Developed but Ageing Low death and birth rates Typical of USA; Sweden; Japan; Britain

Limitations of Demographic Transition Theory:

Limitations of Demographic Transition Theory 1. Birth rates in several MEDCs have fallen below death rates (Germany, Sweden). This has caused, for the first time, a population decline which suggests that perhaps the model should have a fifth stage added to it. 2. The model assumes that in time all countries pass through the same four stages. It now seems unlikely, however, that many LEDCs, especially in Africa, will ever become industrialized. 3. The model assumes that the fall in the death rate in Stage 2 was the consequence of industrialization.

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The timescale of the model, especially in several South-east Asian countries such as Hong Kong and Malaysia, is being squashed as they develop at a much faster rate than did the early industrialized countries. 4. Countries that grew as a consequence of emigration from Europe (USA, Canada, Australia) did not pass through the early stages of the model. Initially, the death rate in many British cities rose, due to the insanitary conditions which resulted from rapid urban growth, and it only began to fall after advances were made in medicine. The delayed fall in the death rate in many developing countries has been due mainly to their inability to afford medical facilities. In many countries, the fall in the birth rate in Stage 3 has been less rapid than the model suggests due to religious and/or political opposition to birth control (Brazil), whereas the fall was much more rapid, and came earlier, in China following the government-introduced ‘one child’ policy.

The Causes of High Fertility : :

The Causes of High Fertility : The Malthusian Population Trap The Micro-economic Household Theory of Fertility

The Malthusian Population Trap:

The Malthusian Population Trap The Malthusian Population Trap Suggests that the population will be forced to live at the subsistence level of income as population growth outstrips growth in the supply of food. Population grows at a geometric rate while food supplies expand only at an arithmetic rate Per capita income would have the tendency to fall so low as to lead to a stable population existing barely at or slightly above the subsistence level. Solutions Preventive checks (birth control, moral restraint) Positive checks (starvation, disease, wars)

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Thomas Malthus argued that because of the natural human urge to reproduce human population increases geometrically (1, 2, 4, 16, 32, 64, 128, 256, etc.). However, food supply, at most, can only increase arithmetically (1, 2, 3, 4, 5, 6, 7, 8, etc.). Therefore, since food is an essential component to human life, population growth in any area or on the planet, if unchecked, would lead to starvation. However, Malthus also argued that there are preventative checks and positive checks on population that slow its growth and keep the population from rising exponentially for too long, but still, poverty is inescapable and will continue.

Limitations of the Malthusian Model :

Limitations of the Malthusian Model 3. They focus on the wrong variable, per capita income, as the pricipal determinant of population growth rates. A much better and more valid approach to the question of population and development centers on the micro economics of family size decision making in which individual, and not aggregate, levels of living become the principal deteminant of a family’s decision to have more or fewer children. They don not take adequate account of te role and impact of technological progess. They are based on a hypothesis about a macro relationship between population gowth and levels of per capita income that does not stand up to imperical testing.

The Micro-economic Household Theory of Fertility :

The Micro-economic Household Theory of Fertility The Micro-economic Household Theory of Fertility People choose how many children to "consume" as part of their utility maximization problem. Children in LDCs can be thought of as investment goods. Demand for children is determined by: Family preferences for a certain number of surviving (usually male) children Price or “opportunity cost” of rearing children (mother’s time to earn, educational attainment of children relative to earning potential) By levels of family income

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The microeconomic theory of fertility is useful here because it asks the question why a family would decide to rear children in the first place. The economics of the family asks what kinds of incentives are involved. After all, the decisions being made are often not based on society’s natural capital, or local wage levels. Family decisions are often made at the microeconomic rather than the macroeconomic level.

Demand for Children Equation:

Demand for Children Equation Where C d is the demand for surviving children Y is the level of household income P c is the “net” price of children P x is price of all other goods t x is the tastes for goods relative to children

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Under neoclassical conditions, we would expect:

The Causes of High Fertility in Developing Countries: The Household Model:

The Causes of High Fertility in Developing Countries: The Household Model The microeconomic household theory of fertility The demand for children in developing countries Some empirical evidence Implications for development and fertility