Demography & population theories

Demography is the statistical study of populations, especially human beings. As a very general science, it can analyze any kind of dynamic living population, i.e., one that changes over time or space (see population dynamics). Demography encompasses the study of the size, structure, and distribution of these populations, and spatial or temporal changes in them in response to birth, migration, ageing, and death. Based on the demographic research of the earth, earth’s population up to the year 2050 and 2100 can be estimated by demographers. Demographics are quantifiable characteristics of a given population.

Demographic analysis can cover whole societies, or groups defined by criteria such as education, nationality, religion and ethnicity. Educational institutions usually treat demography as a field of sociology, though there are a number of independent demography departments. Formal demography limits its object of study to the measurement of population processes, while the broader field of social demography or population studies also analyzes the relationships between economic, social, cultural and biological processes influencing a population.

The reluctance of policy-makers to incorporate detailed demographic analyses in policy analyses often means that population composition is ignored in state and local policy evaluations. This article uses standard demographic projection, standardization and rate decomposition techniques to examine the implications of changing population composition for the property tax revenue base of Texas. The authors find that if current socioeconomic differentials persist into the future, projected compositional changes in the household population of Texas will significantly impact property tax revenues. Thus revenue projections based on aggregate growth and current average property value would seriously overestimate future property tax revenues in Texas because changes in the composition of the population lead to disproportionate growth in households likely to live in lower valued housing units. The results indicate that the continuing focus of state and local policy-makers on changes in population size alone may be ill-advised and demonstrate the increasing importance of local- and state-level demographic analysis in a period of increasing Federal devolution of service provision.

Science of population

Populations can change through three processes: fertility, mortality, and migration. Fertility involves the number of children that women have and is to be contrasted with fecundity (a woman’s childbearing potential). Mortality is the study of the causes, consequences, and measurement of processes affecting death to members of the population. Demographers most commonly study mortality using the Life Table, a statistical device which provides information about the mortality conditions (most notably the life expectancy) in the population. Migration refers to the movement of persons from a locality of origin to a destination place across some pre-defined, political boundary. Migration researchers do not designate movements ‘migrations’ unless they are somewhat permanent. Thus demographers do not consider tourists and travelers to be migrating.

Demography is today widely taught in many universities across the world, attracting students with initial training in social sciences, statistics or health studies. Being at the crossroads of several disciplines such as sociology, economics, epidemiology, geography, anthropology and history, demography offers tools to approach a large range of population issues by combining a more technical quantitative approach that represents the core of the discipline with many other methods borrowed from social or other sciences. Demographic research is conducted in universities, in research institutes as well as in statistical departments and in several international agencies.

Importance of Demography

With the majority of developing countries facing population explosion, the study of population and its problems has become very important in every sphere of an economy. We discuss them below:

• For the Economy: Population studies help to know how far the growth rate of the economy is keeping pace with the growth rate of population. Rapid population growth reduces per capita income, lowers the standard of living, plunges the economy into mass unemployment, brings environmental damage and puts a burden on social infrastructure. These problems can be addressed by government through appropriate measures.
• For Society: When population is increasing rapidly, shortages of basic services like water, electricity, transport, public health, education, etc. arise. Problems of migration and urbanisation lead to law and order issues. State and non-government organisations can adopt appropriate measures.
• For Economic Planning: Data relating to population trends help planners in formulating policies, fixing targets for agricultural and industrial products, schools, hospitals, electricity, etc. Population data are used to project future trends in fertility, labour force, and employment generation.
• For Administrators: In under-developed countries, almost all social and economic problems are associated with population growth. Administrators tackle problems like migration, urbanisation, shanty towns, pollution, drainage, water supply, health services, slum clearance, and education.
• For Political System: Census figures are used for demarcation of constituencies, determining number of voters, and understanding voter composition (male/female, education, age, etc.). Political parties use this data to raise issues and election commissions to establish polling booths and staff.

Methods of Data Collection

To derive conclusions from data, we need to know how the data were collected; that is, we need to know the method(s) of data collection. Four main methods:

• Census: A study that obtains data from every member of a population. In most studies, a census is not practical, because of the cost and/or time required.
• Sample survey: A study that obtains data from a subset of a population, in order to estimate population attributes.
• Experiment: A controlled study in which the researcher attempts to understand cause-and-effect relationships by controlling assignment of subjects and treatments.
• Observational study: Attempts to understand cause-and-effect relationships but without control over assignment of subjects to groups or treatments.

Data Collection Methods: Pros and Cons

• Resources: When population is large, a sample survey has a big resource advantage over a census (quicker, cheaper, less manpower).
• Generalizability: Requires random selection. Observational studies do not feature random selection, so generalizing can be problematic.
• Causal inference: Experiments (random assignment) are the best method for investigating causal relationships.

How census data can be used for development planning

In many countries, the population census plays a major role in the allocation of elected political seats and government resources. For planners, census information is used in just about all planning decisions. The census of population provides information on age and sex distribution, household composition, etc., vital for determining needs. The census of housing allows planners to assess changes in housing quality and plan future needs.

Malthus’ Theory: Thomas Robert Malthus (1766-1834) was the key figure to analyse the population statistics. In his Essay on the Principle of Population (1798) Malthus argued that because of the strong attraction of the two sexes, the population could increase by multiples, doubling every twenty-five years. He contended that the population would eventually grow so large that food production would be insufficient. Human capacity for reproduction exceeded the rate at which subsistence from the land can be increased. Malthus further wrote: “Population when unchecked increases in a geometrical ratio. Subsistence increases only in an arithmetical ratio.”

Malthus contended that the world’s population was growing more rapidly than the available food supply. He argued that the food supply increases in an arithmetic progression (1, 2, 3, 4…), whereas the population expands by a geometric progression (1, 2, 4, 8…).

In brief, Malthus theory states that: (1) Population is necessarily limited by the means of subsistence. (2) Population invariably increases where means of subsistence increased, unless prevented by some very powerful and obvious checks. (3) These checks, which repress the superior power of population and keep its effects on a level with the means of subsistence, are resolvable into moral restraint, vice and misery.

Malthus based his arguments on man’s two basic characteristics: (i) the need for food, and (ii) the passion between sexes. It was the second which led people to marry early and result in large numbers of births, doubling population in few years if unchecked by misery and vice.

Checks on population

• Positive means: famine, disease, war, pestilence, vicious customs.
• Negative means (preventive): late marriage (postponing marriage until later age), moral restraint, chastity (abstinence). He explicitly demanded artificial means of birth control? — Malthus was not in favour of contraception; he preferred moral restraint as it generated a drive to work hard. Without such restraints the world would face widespread hunger, poverty and misery.

The ‘positive’ and ‘preventive’ checks relate to practices affecting mortality and fertility respectively. Malthus saw tension between population and resources as a major cause of misery.

Theory of Demographic Transition (introduction)

Demographic transition is a term, first used by Warren S. Thompson (1929), and later by Frank W. Notestein (1945), referring to a historical process of change which accounts for trends in births, deaths and population growth in today’s industrialized societies. It is not a ‘law of population growth’ but a generalized description of the evolutionary process. It attempts to specify general laws by which human populations change in size and structure during industrialization.

The theory postulates a particular pattern: from high fertility and high mortality to low fertility and low mortality when a society progresses from rural agrarian to urban industrial. It is typically viewed as a three-stage process (some scholars like Haggett divide into four or five stages):

• Pre-transition / Stage I: High and fluctuating birth and death rates, little population growth.
• Stage II (population explosion): High birth rates and declining death rates → rapid population growth.
• Stage III: Low birth and death rates → slow population growth.
• Stage IV (sometimes added): Birth and death rates both low, near balance, zero or slow growth.

The growth pattern is thus S‑shaped, involving transition from one stability (high death/high birth) to another (low death/low birth). In the present world, different countries are at different stages due to cultural diversity.

Theory of Demographic Transition throws light on changes in birth rate and death rate and consequently on the growth-rate of population. Along with economic development, tendencies of birth-rate and death-rate are different. According to E.G. Dolan, “Demographic transition refers to a population cycle that begins with a fall in the death rate, continues with a phase of rapid population growth and concludes with a decline in the birth rate.” Economic development has the effect of bringing about a reduction in the death rate. C.P. Blacker divided populations into five types: high stationary, early expanding, low stationary, diminishing, etc.

Four stages (as per Max / usual exposition):

• First stage (high growth potential): high and fluctuating birth & death rates, rural agrarian society, low income, poor sanitation, high mortality, population roughly stable.
• Second stage (population explosion): death rate declines (better medicine, sanitation, productivity), birth rate remains high → rapid growth. Economic development speeds up but attitudes unchanged.
• Third stage: birth rate begins to fall (social change, family planning), death rate low, population still grows but at diminishing rate.
• Fourth stage (stationary): low birth rate and low death rate, population becomes stable or slow-growing.

Causes behind slow demographic transition in Pakistan

Pakistan remains in the second or early third stage of demographic transition. Several factors contribute to slow transition:

• Persistently high fertility: Due to low female literacy, early marriages, preference for large families, and limited access to family planning services in rural areas.
• Declining but still significant mortality: Infant and child mortality have decreased, but not enough to trigger rapid fertility decline; cultural norms still encourage higher births as insurance against child deaths.
• Inadequate healthcare infrastructure: Although death rates have fallen, maternal and child health services remain insufficient, and awareness about contraception is low.
• Socio-economic factors: High poverty, low education levels (especially among women), and strong patriarchal norms slow the adoption of smaller family norms.
• Urbanisation without attitudinal change: While urban areas grow, many migrants retain rural fertility preferences. The expected fertility decline linked to urban living is dampened by poverty and lack of female employment.
• Weak implementation of family planning programs: Despite policy commitments, programs suffer from inconsistent funding, cultural resistance, and insufficient outreach.
• Religious and cultural beliefs: In some communities, contraception is discouraged, and large families are seen as a sign of prestige and economic support.

As a result, Pakistan’s population continues to grow at around 2% annually, slowing the potential economic and social dividends of transition.