PHS 204: Sources and Nature of Population Data

Meaning and Nature of Demographic Data

  • Definition of Demographic Data:

    • Demographic data refers to information regarding groups of people categorized by specific attributes. These attributes include age, sex, and place of residence.
    • It encompasses socioeconomic factors expressed statistically, such as occupation, family status, income level, employment, education, marriage rates, and birth and death rates.
    • The primary variables gathered in demographic research include:
      • Age
      • Sex
      • Income level
      • Race
      • Employment status
      • Geographic location
      • Homeownership status
      • Level of education

  • Demographic Analysis and Generalizations:

    • Demographic analysis is defined as the study of a population based on factors like age, race, and sex.
    • This information is used to make generalizations about groups, which is often utilized to identify customers or target populations.

  • Nature and Scope of Demography:

    • Demography is the "science of populations."
    • Demographers investigate three main demographic processes to understand population dynamics: birth, migration, and aging (which includes death).
    • Key parameters influencing population growth or decline include:
      • Population size
      • Population density
      • Age structure
      • Fecundity (birth rates)
      • Mortality (death rates)
      • Sex ratio

Sources of Demographic Data

  • The Three Main Sources:

    • Censuses
    • Surveys
    • Administrative Records
    • These sources form part of an integrated program for data collection and compilation. Together, they provide comprehensive information for policy formulation, development planning, administrative purposes, research, and commercial use.

  • Population Census:

    • Definition: A total process involving the collecting, compiling, evaluating, analyzing, and publishing/disseminating of demographic, economic, and social data pertaining to all persons in a country (or a well-delimited part of a country) at a specified time.
    • Usefulness:
      • Collects data from every individual and living quarter in a whole country.
      • Allows for estimates for small geographic areas and population subgroups.
      • Provides base population figures used to calculate vital rates from civil registration data.
      • Supplies the sampling frame for sample surveys.
    • Requirements for a Credible Census: A census must be carefully planned and executed due to the complexity of covering an entire population in a short time. Pre-implementation activities include:
      • (a) Securing legislation, political support, and funding.
      • (b) Mapping and listing all households in all areas for enumeration.
      • (c) Planning and printing questionnaires, manuals, and procedures.
      • (d) Establishing logistics for shipping census materials.
      • (e) Recruiting and training all census personnel.
      • (f) Organizing field operations.
      • (g) Launching publicity campaigns.
      • (h) Preparing for data processing.
      • (i) Planning for tabulation, production, and dissemination of results.

  • Household Surveys:

    • Nature: These represent a continuing program of intercensal surveys useful for gathering detailed social, economic, and housing characteristics not suitable for a full-scale census.
    • Flexibility: Household surveys are the most flexible of the three sources; almost any subject can be investigated through them. They can examine subjects in greater detail because the workload is smaller and personnel can be trained more intensively.
    • Usefulness:
      • Meet emerging data needs on a continuing basis.
      • Facilitate the training and experience of in-house technical and field staff.
      • Maintain resources like maps, sampling frames, and infrastructure.
    • Types of Surveys: Multi-subject, specialized, multi-phase, and panel or longitudinal surveys.
    • Examples:
      • National Demographic Health Survey (NDHS).
      • National Family Health Surveys.

  • Administrative Records (Vital Statistics):

    • Definition: Statistics compiled from administrative processes. This include vital events from civil registration (births, deaths, marriages, divorces, separations, annulments, adoptions) and records from institutions (school records, hospital health records, employment extension services).
    • Value: Many social statistics are produced as a by-product of these processes (e.g., education statistics from Ministry of Education reports).
    • Reliability Factors: Usefulness depends on the completeness of coverage and the compatibility of concepts and definitions with those used in the census.

Combining Data Sources

  • A combination of two or all three sources is often used to obtain the most accurate estimates.
  • Countries use multiple sources when statistics are critically important for policy and development but no single source provides sufficient reliability.
  • Cost Considerations: While employing multiple sources increases accuracy, it also increases costs. National statistical authorities restrict this practice to highly critical statistics.
  • Example: In developing countries, fertility data is often collected through all three sources to better estimate levels and trends, even if results vary between sources.

Historical Perspectives and Theories

  • Human Population Growth:

    • Population was historically stable until innovation and industrialization made food, energy, water, and medical care more reliable.
    • Applying a population perspective to health involves asking why a population has a specific risk distribution, rather than just why an individual became ill.

  • Malthusian Theory of Population:

    • Proponent: Thomas Robert Malthus.
    • Core Concept: The theory posits exponential population growth vs. arithmetic growth of the food supply.
    • Checks: Malthus believed a balance could be established through "preventive" and "positive" checks.

The Demographic Transition Theory (DTT)

  • Origins: Propounded by W.S. Thomson and F.W. Notestein.

  • Core Argument: Societies progress from a pre-modern regime of high fertility and high mortality to a post-modern regime of low fertility and low mortality.

  • Mechanism: The transition is largely driven by a reduction in death rates through the control of epidemic and contagious diseases.

  • Impact: It results in a substantive change in the age distribution of a population over the long term.

  • The Five Stages of the Demographic Cycle:

  1. First Stage (High Stationary):

    • Pre-industrial / pre-transition stage.
    • Characterized by high birth rates and high death rates.
    • Population remains stationary.
    • Occurs when a country is economically weakest. No countries are currently classified in this stage.

  2. Second Stage (Early Expanding):

    • Characterized by a declining death rate while the birth rate remains high.
    • Death rate decline is due to improvements in food supply, health care, and sanitation.
    • Results in a "huge increase" in population.
    • Examples: Poorest countries such as Afghanistan, Bolivia, Niger, Pakistan, Uganda, Yemen, and Palestine Territories.
    • Note: Nigeria is said to be in this stage (though arguable). Birth rates in some countries in this stage have increased due to improved healthcare and shorter breastfeeding periods.

  3. Third Stage (Late Expanding):

    • Death rate declines further; birth rate begins to fall.
    • Population still increases because Birth Rate (BR) > Death Rate (DR).
    • Falling BR is attributed to access to contraceptives and women's empowerment.
    • Examples: India, South Africa, Colombia, Mexico, Botswana, Jamaica, Kenya, and UAE.

  4. Fourth Stage (Low Stationary):

    • Low birth rate and low death rate.
    • Natural growth is low; the population remains stationary.
    • An aging population is a characteristic feature.
    • Population pyramid looks like a rectangle due to even age distribution.
    • Examples: Canada, Argentina, China, Singapore, South Korea, Brazil, Australia, Denmark, Belgium, UK, and USA.
    • Zero Population Growth: Recorded in Austria between 1980–1985.

  5. Fifth Stage (Declining):

    • Birth rate falls below the death rate.
    • Population begins to decline.
    • Examples: Croatia, Estonia, Germany, Greece, Hungary, Japan, Norway, Portugal, and Ukraine.
  • Causes of Transition:
    • Rise in demand for human capital.
    • Impact of the declining gender wage gap during the 19th and 20th centuries.

Statistical Representations (Summary)

  • Population growth is visually represented as the area between the Birth Rate and Death Rate curves.
  • Births and deaths are typically measured as rates per 1000 per year (Rate/1000/Year\text{Rate/1000/Year}).