Some Theories and Concepts in Demography

The Malthusian Theory of Population Growth

Thomas Robert Malthus, an English political economist, put forward one of the most famous theories in demography in his Essay on Population (1798). His outlook was deeply pessimistic. Malthus argued that human populations grow at a much faster rate than the means of subsistence — especially food, but also clothing and other agriculture-based products. Because of this, humanity is condemned to live in poverty forever, since agricultural production will always be overtaken by population growth.

The core of his argument rests on two different growth rates. Population, Malthus said, rises in geometric progression — like 2, 4, 8, 16, 32, and so on. Agricultural production, however, can only grow in arithmetic progression — like 2, 4, 6, 8, 10. Since population growth always outstrips the growth of subsistence resources, the only way to increase prosperity is to control population growth.

Malthus believed that humanity has only a limited ability to voluntarily reduce population growth. He called these voluntary measures preventive checks — postponing marriage, practising sexual abstinence, or celibacy. Because these were insufficient, Malthus argued that positive checks were inevitable. These are nature's way of dealing with the imbalance between food supply and population: famines and diseases. In his own dramatic words, quoted in the textbook, "premature death must in some shape or other visit the human race" — through vice, epidemics, pestilence, plague, and finally "gigantic inevitable famine."

Why Malthus Was Proved Wrong

The most effective refutation came from the historical experience of European countries. By the latter half of the nineteenth century, the pattern of population growth began to change. By the end of the first quarter of the twentieth century, the changes were dramatic: birth rates had declined, and outbreaks of epidemic diseases were being controlled. Malthus's predictions were proved false because both food production and standards of living continued to rise despite rapid population growth.

Two main lines of criticism emerged:

• Liberal and Marxist scholars argued that Malthus was wrong to assert that poverty was caused by population growth. Instead, they pointed to the unequal distribution of economic resources. An unjust social system allowed a wealthy and privileged minority to live in luxury while the vast majority were forced into poverty. Poverty and starvation, they said, were caused by this inequality, not by population growth itself.

• Technological and economic progress showed that economic growth could outstrip population growth. The textbook's Activity 2.1 asks students to consider how agricultural productivity increased substantially — through better farming methods, new technologies, and other factors — which Malthus had not anticipated.

The Theory of Demographic Transition

This is another significant theory in demography. It suggests that population growth is linked to overall levels of economic development, and that every society follows a typical pattern of development-related population growth. The theory identifies three basic stages.

Stage One: Low Population Growth (Underdeveloped, Backward Society)

Both the death rate and the birth rate are very high. Because both are high, the difference between them — the net growth rate — is low. So population growth is low, but for very different reasons than in a developed society.

Stage Three: Low Population Growth (Developed Society)

Both death rate and birth rate have been reduced considerably. The difference between them is again small, so population growth is low. This is the stage of a developed, prosperous society.

Stage Two: The Transitional Stage (Population Explosion)

This is the stage of movement from a backward to an advanced society. It is characterised by very high rates of population growth — a population explosion. Why does this happen?

Death rates are brought down relatively quickly through advanced methods of disease control, public health measures, and better nutrition. However, it takes much longer for society to adjust its reproductive behaviour. People's childbearing habits were evolved during a period of poverty and high death rates, and they do not change overnight. So birth rates remain high while death rates fall sharply, producing a huge gap between them and very rapid population growth.

This pattern was observed in Western Europe during the late nineteenth and early twentieth century. Similar patterns are followed in less developed countries today, which are struggling to reduce birth rates in keeping with falling mortality rates. In India, the demographic transition is not yet complete — mortality has been reduced, but the birth rate has not been brought down to the same extent.

Common Concepts and Indicators in Demography

Most demographic concepts are expressed as rates or ratios. They involve two numbers: one is the particular statistic calculated for a specific geographical-administrative unit, and the other provides a standard for comparison.

Birth Rate and Death Rate

The birth rate is the total number of live births in a particular area (a country, state, district, or other territorial unit) during a specified period (usually a year), divided by the total population of that area in thousands. In other words, it is the number of live births per 1000 population.

The death rate is similar: the number of deaths in a given area during a given time per 1000 population.

Both these statistics depend on the reporting of births and deaths by the families in which they occur.

Rate of Natural Increase (Growth Rate)

This refers to the difference between the birth rate and the death rate. When this difference is zero — or, in practice, very small — we say that the population has stabilised or has reached the replacement level. This is the rate of growth required for new generations to replace the older ones that are dying out.

Sometimes societies experience a negative growth rate — their fertility levels are below the replacement rate. This is true of many countries and regions today, such as Japan, Russia, Italy, and Eastern Europe.

Fertility Rate

The fertility rate refers to the number of live births per 1000 women in the child-bearing age group, usually taken as 15 to 49 years. Like the birth and death rates, this is a crude rate — it is a rough average for an entire population and does not take into account differences across age groups. These differences can sometimes be very significant, which is why demographers also calculate age-specific rates.

Infant Mortality Rate and Maternal Mortality Rate

The infant mortality rate is the number of deaths of babies before the age of one year per 1000 live births. The maternal mortality rate is the number of women who die in childbirth per 100,000 live births.

High rates of infant and maternal mortality are an unambiguous indicator of backwardness and poverty. Development is accompanied by sharp falls in these rates as medical facilities, levels of education, awareness, and prosperity increase.

Life Expectancy

This refers to the estimated number of years that an average person is expected to survive. It is calculated on the basis of data on age-specific death rates in a given area over a period of time.

Sex Ratio

The sex ratio refers to the number of females per 1000 males in a given area at a specified time period.

Historically, all over the world, it has been found that there are slightly more females than males in most countries. This is despite the fact that slightly more male babies are born than female ones — nature seems to produce roughly 943 to 952 female babies for every 1000 males. If despite this the sex ratio is somewhat in favour of females, it seems to be due to two reasons:

• Girl babies appear to have an advantage over boy babies in terms of resistance to disease in infancy.
• At the other end of the life cycle, women have tended to outlive men in most societies, so there are more older women than men.

The combination of these two factors leads to a sex ratio of roughly 1050 females per 1000 males in most contexts.

However, the sex ratio has been declining in some countries like China, South Korea, and especially India. This phenomenon has been linked to prevailing social norms that value males much more than females, leading to son preference and the relative neglect of girl babies.

Age Structure …