TYPES AND SOURCES OF POPULATION DATA

1. TYPES AND SOURCES OF POPULATION DATA BY Dr. J. Kivelia Department of Geography UNIVERSITY OF DAR ES SALAAM

2. Outline • Introduction – The need for population data • Nature/Types of population data • Sources of Population data • Censuses • Surveys • Vital registers

3. Introduction • Demographic data are used to analyse population dynamics • Population data form an important foundation of the planning process in many countries. • Therefore it is important to know the various types and sources of demographic data. • Equally important to detect the main errors and biases contained in the in the data.

4. Contd. • The Government and other institutions generate demographic data. • Demographic data must be of good quality • The uantity of data generated depends on: • the main objective of collecting this data, • the sources, • the overall attitudes of the population in providing this data, • the accuracy of recording and processing.

5. The need for demographic data • Demographic data is essential for planning purposes like: • to plan for socio-economic needs • power, water, transport, health, education and shelter. Productiopn of material goods, etc. • to determine the level of electoral representation.

6. Types of demographic/Population data • Demographic data – size (number), age, sex • Vital events – births, deaths & migrations • Socio-cultural data – marital status, education, occupation/employment, disability, etc.

7. Sources of Demographic Data • There are three main sources of demographic data which are: • Censuses, • Sample surveys, and, • Vital registrations.

8. Censuses • A census is defined as the total process of collecting, compiling and publishing demographic, economic and social data pertaining at a specified time to all people in a country or specified territory. • It involves a series of activities spanning over a long time; on most occasions up to five years. • It requires much resources and personnel.

9. Contd. • After collecting the data the tabulation and publications also requires much money. • The census remains to be the main source demographic data in most developing countries.

10. Characteristics of a census • A census must fulfill the following characteristic conditions: • Sponsorship • Universality • Simultaneity • Individuality • Periodicity

11. Characteristics of a Census • 1. Sponsorship: A census is usually sponsored by the national government. • The government provides and mobilizes the resources from various sources especially partners in development like UNFPA. • It requires adequate legislation support or legal authority

12. Contd. • 2. Universality within a defined territory: Enumeration must cover every person within a defined territory or geographic unit eg. A state, country, region. • 3. Simultaneity: For census data to have any comparative logic a census should be taken simultaneously in the whole country. Best practice is on one defined night.

13. Contd. • 4. Individuality: refers to individual enumeration where every individual must be enumerated separately. It is only on rare occasions when group enumeration is used e.g. prisons and other armies. • 5. Periodicity: A census should be in a defined period of time at constant intervals say 5 or 10 years so that the information becomes comparable between periods and between populations. E.g. Censuses in Tanzania: 1948, 1957/1958, 1967, 1978, 1988, 2002 and 2012.

14. Enumeration approaches • Enumeration refers to counting the people within recognized geographical boundaries. • There are two types of enumerations: • De facto • De jure

15. Contd. • 1. De facto: seeks to obtain information of all persons according to where they were found during the census day or census night. • 2. De jure: enumerates individuals’ data according to the place of usual residence.

16. Census Errors • Although many censuses have been taken there are several errors especially in developing countries. These are: • Content errors • Coverage errors • Content errors are errors which occur during any stage of collecting data e.g. Response errors, recording errors, editing of questionnaires, coding errors and data compiling processes.

17. Contd. • Coverage errors are errors occurring because of incomplete coverage of the enumeratin process. This can occur because: • an area within the enumeration region is missed • some groups like the homeless • Some households are missed out within an enumeration area • Some individuals are missed out in the enumerated households

18. Data Processing and Tabulation • Data processing is needed for economic and social planning • The data must be prepared in well understood tables or friendly usable.

19. Publications and Dissemination Plans • Census publications should fulfill the needs of the expected users and at the same should be economical, timely and of good quality.

20. Merits of Censuses • It does not suffer from sampling errors because it covers the whole country or region. • The results can be easily compared with the results of other censuses in other countries because of its universality. • Since it is taken at regular intervals it is the most popular source of demographic data.

21. Demerits • It is an expensive exercises which necessitates some developing countries not carry it out. • May be postponed due to lack of money e.g. Tanzania 1978 and 1998. • It is difficult to collect detailed information because it covers the whole country.

22. Sample Surveys • It is the information which is collected from a sample of the population. • The sample is obtained by through various probability sampling techniques such as: • simple random sampling, • stratified sampling, • cluster sampling, • systematic sampling, and, • multistage sampling.

23. Contd. • The objectives of taking a sample are diversified but most of them intend to take a sample of a population so that it represents accurately the whole population. • It must represent the true characteristics of the population. • Before any sampling is done it is important to draw a sampling frame which can be divided into strata or specified groups according to the needs of the survey.

24. Contd. • Stratification allows for the sampling of small but significant sub-populations. • Types of sample surveys include: • (a) The single-round survey- involves only one interview with the respondents e.g. World Fertility Surveys in the 1970s and 1980s and Demographic and Health Surveys in the 1990s to the present.

25. Contd. • 2. The Multi-round Survey: the survey design allows for the possibility of re-interviewing the same respondent several times e.g. Household Surveys and Labour Force Surveys in Tanzania

26. Merits of Sample Surveys • 1. Sample surveys are simple to carry out and administer. • More flexible than censuses. • It has relatively low cost • More detailed information is collected

27. Demerits of Sample Surveys • 1. They are not free from sample errors. • 2. Not easy to compare from one country to another.

28. VITAL REGISTRATIONS • The tradition began several centuries ago in China. • Earliest registration data was obtained from Parish Registers of pre-industrial Europe. • As early 1935 every priest in England was required to make weekly registration of baptism, marriage and death (burials).

29. Contd. • This occurred decades before the registration system was established throughout the country. • The first compulsory civil registration system started in I Scandinavia in the 17th century. • Later spread to Europe and North America in the 19th century.

30. Contd. • Nowadays the registration is more established in developed countries where it has assumed legal dimensions and gives specialized data in many social aspects. • Formally it covered births and deaths but nowadays embraces events such as marriage, adoption, annulments, legitimizations, separation, divorce and migration.

31. Contd. • The system requires a well established system of collecting data on some or all these events. • Hence it is limited in developing countries like Tanzania where it is a rudimentary stages in rural areas. • Village registers is an attempt to develop the registration system.

32. Merits and Demerits • A better substitute of a census if it is not marred by political ambitions. • Demerit- expensive as a system because it has to cover the country to village level.

33. Food for thought • Outline the main strengths and weaknesses of: • Censuses • Sample surveys • Vital Registration Systems • Differentiate between de facto and de jure approaches of censuses • Comment on the applicability of Vital Regisstration Systems in developing and developed countries