Question

Demographic transition:

a) What are four of the causes for the demographic transition?

b) Does the demographic transition confirm or refute Malthus’ predictions about development and population?

c) Why do death rates fall BEFORE birth rates fall and what does this imply for population growth?

Answer 1

a.

Mortality

There has been a large decreases in mortality over the last 300 years and they have mainly been due to advances in health knowledge that lead to the prevention and treatment of infectious diseases. Even the poorest developing countries today have seen rapid improvements in health over the last 50 years. The caveat to this, of course, is the HIV/AIDS epidemic which has led to sharp reductions in life expectancy in many countries in Sub-Saharan Africa. While this picture of health improvements being largely exogenous seems true today, this may not have been the case for health improvements in the 18th and 19th centuries. This is linked to the debate about the relative importance of nutrition, which is endogenous and income dependent, and public health measures due to exogenous advances in health knowledge in historical mortality improvements. It is clear that the mortality transition first started in richer countries and spread to poorer countries over time.

Fertility

Fertility is influenced by government policy, contraceptive availability, education, ideation, and culture, the central underlying cause of the fertility transition is the prior mortality transition. The strongest evidence for this is the fact that the fertility decline always follows the decline in mortality. Against this, the initial response to the start of the mortality decline is a rise in fertility and the very rapid fertility transition in some countries in recent years relative to historical episodes means the relationship may not be automatic. There is undoubtedly an effect of lower child mortality on desired fertility. The increase in child survival rates reduces fertility required to achieve a desired number of surviving children. An alternative explanation is the economic model which emphasizes fertility decisions as being the result of a quantity quality tradeoff. A key is the returns to education n and human capital. If technological progress raises the returns to schooling, families may decide to have fewer children but invest more in each child. A third idea is that advances in contraceptive technologies have played a key role in allowing the reduction in fertility.

Urbanization

Prior to the demographic transition high mortality in cities tended to give them an excess of deaths over births and they were sustained only by rural to urban migration. As mortality declined the death rates in cities fell below the death rate in rural areas. The urban population became self sustaining though urbanization, meaning the increasing proportion of people in urban areas, requires continuing rural to urban migration.

The Quality of People

A remarkable feature of the modern era is the increase in the “quality” as well as quantity of people. In economics, quality or human capital has been taken to be synonymous with education but we should think of the quality of people in a broader sense. Over the last 100 years we have seen substantial increases in the physical and cognitive development of children, as evidence by gains in adult heights and IQ scores even in the component not associated with education. These gains have been due to improvements in nutrition and health in the first few years of, the mortality transition that sets off the demographic transition is also usually a health transition that is associated with better nutrition and a lower burden of disease.

b. The demographic transition has swept the world since the end of the nineteenth century. The unprecedented increase in population growth during the Post-Malthusian Regime has been ultimately reversed, bringing about significant reductions in fertility rates and population growth in various regions of the world.

The demographic transition has enabled economies to convert a larger portion of the gains from factor accumulation and technological progress into growth of income per capita. It enhanced labor productivity and the growth process via three channels. First, the decline in population growth reduced the dilution of the growing stocks of capital and infrastructure, increasing the amount of resources per capita. Second, the reduction in fertility rates permitted the reallocation of resources from the quantity of children toward their quality, enhancing human capital formation and labor productivity. Third, the decline in fertility rates affected the age distribution of the population, temporarily increasing the fraction of the labor force in the population and thus mechanically increasing productivity per capita.

c. The changes in the population of countries over time have been found to follow a pattern described as ‘demographic transition’. Demographic transition is a process of fundamental change by which a country moves gradually from high birth and death rates to low birth and death rates. During the transition, death rates decline first and this is followed by a decline in birth rates.

The rate of natural increase of a population depends on birth and death rates, which are strongly influenced by the population age structure. Births occur primarily to people in the younger-adult age groups. If there are comparatively more young adults than older adults where mortality is highest, then even at replacement fertility levels (when each woman has about an average of two children) there will be more births than deaths.

Hence, a relatively large number of couples each having one or two children can still produce a large excess of births. This phenomenon is known as population momentum.

The momentum of population growth in less developed countries will only be slowed when the large number of young adults resulting from previous high fertility have passed out of the childbearing years and a succeeding smaller generation reproduces at replacement level fertility. This momentum is very pronounced in China, where women have about two children, but the number of women having children is now much larger than in the previous generation. Thus, even though it has reached replacement level fertility, China’s population continues to grow.