Demography: Definition, Examples, Importance of Demography

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Demography Definition

Demography is a systematic study or body of knowledge that has been derived through the scientific application of knowledge to answer population problems. It involves the application and usage of materials which include: gathering and organizing of data, manipulation of data, analysis, description and interpretation of data which are related to members, geographical distributions, characteristics, vital processes and changing numbers over space and time of human beings.

A student of population geography is a demographer. According to Hausar and Duncan, 1976, the study of demography is the study of the size, territorial distribution and the composition of the population and the changing theories that take place in such things as; fertility, mortality territorial movements (migration), social mobility and change of status.

Michael Drake in 1972 stated that demography is that discipline that looks at the general population characteristics and their interaction within a given geographical space. It is a scientific body of knowledge that have been derived through scientific. It involves the gathering and organization of population.

Demography is a science of human populations. For much of the preceding 400 years, the field has concerned itself with the size, distribution and composition of populations, and how changes in these are connected with the three population processes of mortality, fertility and migration (Greenhalgh, 1996). While formal demography has developed mathematical and actuarial techniques to model and project changes in population, the interdisciplinary field of population studies examines demographic change within its broader societal setting and makes use of a wide range of approaches. Despite its keen interest in population distribution, its interdisciplinary niche and its strong connections with sociology and economics, demography has had a relatively limited engagement with geography. Although the development of population geography between the 1960s and the 1980s and the growth of spatial demography drew attention to the study of mortality, fertility and particularly migration, many geographical analyses of issues including poverty, gender roles, social exclusion, urbanization and environmental degradation underplay population factors. Descriptions of changes in population size and distribution make use of empirical data on deaths, births, moves and the ages at which these events occurred, mostly obtained from population censuses, social surveys or registers of population.

Characteristics of Demography

Demographers are mainly concerned with the following characteristics.

  • Age- age is the most vital characteristics or composition of the population, the age determines ones behaviour and each specific age group.
  • Sex- it tells us about the ratio of men to women. Age also tells us about the ratio of women who produce the next generation of children. It also tells us about the age sex pyramid.
  • Migration- this deals with the rate at which population are being added or reduced from a geographical area. It is equally interested in fertility and mortality characteristics.

Demographic transition

Demographic transition is a framework that explores the historical sequence of changes in fertility, mortality, migration and age structure. This cornerstone of research in demography uses widely accessible data (typically, time series records of vital rates), proposes that stages of economic development have particular demographic signatures and suggests that population policies encourage zero population growth. Its foundational concepts celled on French and western European experience in the nineteenth and early twentieth centuries, and described a linked reduction in mortality rates that helped to trigger sustained declines in birth rates.

According to the classic transition model, populations began at a high stationary phase, with both death rates and birth rates high, and overall population growth rates low. Improvements in fresh water supply and sanitation, public health and nutrition (characteristics of the epidemiological transition) begin to support a downward trend in death rates. As this occurred at the same time as birth rates remained high, population growth accelerated during the next early expanding phase. During the third late expanding phase, population growth continued but annual rates of increase slowed down as the linked fertility transition kicked in and birth rates fell in response to diverse factors including urbanization, decreased infant mortality, the changing roles of children and women in society, contraception, and new patterns of nuptuality (Sanderson and Dubrow, 2000). Finally, populations entered a low stationary phase, where both birth and death rates are low, and natural increase is again close to zero. Considerable research has examined the degree to which, given time, all regions of the world will exhibit vital signs and demographic mechanisms that converge on this ideal type (Coleman, 2002). For example, across contemporary sub-Saharan Africa, there is evidence to both support the diffusion of the transition and question the transitions assumption of universalism. Indeed, sensitivity to both historical and spatial variations in linked demographic transitions has led to calls for a reformulation of the classic framework. Noting very high levels of ageing and below replacement fertility across a number of more developed nations, advocates of a new and distinctive second demographic transition discussed how new links between demographic drivers are being shaped by the changing relationships between parents and children in society, new living arrangements (including increased rates of cohabitation, mixed marriages and divorce) and sexual behaviours (including later parenting and high fertility outside marriage). In turn, the rise of immigration for example, in response to below replacement fertility may promote new modes of belonging and family strategies, and create the conditions for another distinctive transition.

Methods of Demographic Data

There three basic methods of or model by which a demographic sample data can be collected, they are:

  1. Active model: in this models, the registration officer would normally go out in search of a place where the demographic events are taking place. He is interested in registering such events . In this case, more people are likely to be registered because the registration officer is following them up and the data is active because it is available for census registration. Example of such registration are censuses, demographic samples surface. The advantages are:
  • More population are registered
  • A wider area is covered
  • The data is more reliable
  • It is better than the passive method
  1. Passive model: in the case of passive model, the registration officers would stay in their offices and expect the respondents to come to them for registration of events that have taken place. When the people do not go out to register, no record of them are found, in passive model, the data are not available, you will be the one to find the registration officer to register for election. Example of this type of registration is the school registrations, hospital registrations or INEC registrations.

This model has more disadvantages which may include:

  • Valuable information may be lost
  • Area of coverage is small which means that a greater proportion of the population is left out
  • Reliability becomes a problem
  1. Active and passive model: in this model, the registration officer would find himself in his office doing the registration of the events as it has been reported to him and at the same time he goes out in search of those events. This models for instance, is able to take care of the disadvantages in the first two models.


  • In this models also, there is a reliability of the information collected.
  • Coverage is wide enough, almost all segments of the population is affected.

Importance of Demography

The study demography is important for the following reasons

  • Advancement of scientific knowledge: that is finding out what happen to the population security, society and the formulation of new theories for testing these theories against the causes of events.
  • It helps to plan ahead: as demographers, there is need to plan ahead in order to satisfy mans needs throughout his life. For example, we have to plan how food, shelter clothing and other necessities of life can be gotten for instance, planning for health facilities, such as building of hospitals, training of doctors and nurses, investigation of diseases and diseases control. Planning for education- building of schools training of teachers production of educational materials. It could also be planning for housing, type of housing quality of housing, housing facilities etc.
  • For political mathematics: we need to plan for political purposes such as elections, formation of political parties, demarcation of political wards, collection of taxes by government, planning for social services, good health facilities, preservation of law and order.
  • Development of policies: The demographer is interested in policies involving legislation, policies that can eliminate position or influence opposition, policies that can influence health, education services etc.