Introduction to demography and biostatistics

1. OSUN STATE UNIVERSITY
LEARNING MANAGEMENT SYSTEM
(VIRTUAL CLASS)
https://lms.uniosun.edu.ng

2. Introduction to demography 3
Population pyramids, Census; types and methods; sources and
quality of data from census, special surveys, and vital and other
registration systems.
January, 2021

3. COM 201: INTRODUCTION TO BIOSTASTICS
AND DEMORAPHY
By
PROF. ESTHER. O ASEKUN-OLARINMOYE

4. •Course code: COM 201
•Course title: INTRODUCTION TO DEMOGRAPHY
AND BIOSTATISTICS
• Course Unit: 2units

5. Outline
•Population pyramids
•Census: types and methods
•Health and Vital Statistics
•Sources and quality of data from
census
• Special surveys
•Vital and other registration systems

6. Demography is the scientific study of the characteristics of human
populations in terms of structure, distribution, growth & developments, and
spatial and/or temporal changes in them in response to birth, migration,
aging and death.
It focuses on :
 changes in population size (growth or decline)
composition of the population (structure – age, sex distribution of
pop)
distribution of population in space.
size of population – total no. of pop present in a geogr. Area.
Three phenomena in Demography
 Changes in population size
 Composition of population
 Population distribution in space

7. Structure
• Structure means the distribution of persons present in the population by
sex and age etc
• Population structure means the 'make up' or composition of a population.
• Looking at the population structure of a place shows how the population
is divided up between males and females of different age groups.
• Population structure is usually shown using a population pyramid.
Composition of Population:
Composition of population covers all the measurable characteristics of the
people who form a given population.
• The most widely used characteristics are age and sex.

8. POPULATION PYRAMID
• The population pyramid is one of the most popular visual representations of
data in demography.
• In its standard form it comprises two histograms rolled on their sides and placed
back-to-back, with the youngest ages at the bottom of the diagram and the
oldest at the top.
• Generally, the male population is placed on the left and the female population
on the right.
• The populations of each age-sex group are shown either as absolute numbers or
as a percentage of the whole population.
• May provide insights about political and social stability, as well as economic
development.
• The male and female populations are broken down into 5-year age groups
represented as horizontal bars along the vertical axis, with the youngest age
groups at the bottom and the oldest at the top.

9. • The shape of the population pyramid gradually evolves over time based on
fertility, mortality, and international migration trends and it offers clues
about a population’s fertility history, mortality and migration, position in
the demographic transition, and the likely influence of its age-sex structure
on future demographic change.
• A population pyramid presents immediately digestible information on the
age-sex structure of a population that would be less obvious in tabular
form.
• This distribution is important for understanding the demand for the wide
range of goods and services which vary by age and sex.
• Population age structure also affects government spending and taxation
• The shape of a population pyramid can hint at the economic or
demographic role of the population in question
• It can also be used to check for potential data problems, such as age
heaping.

10. • The size of any age group shown in a standard population pyramid
equals the original number of births of the cohort, minus the number
of deaths which have occurred between birth and the reference date
of the pyramid, plus the net balance of inward and outward migration
experienced over the same age-time space.
• The shape of a population pyramid can tell us a lot about an area's
population.
• It gives us information about birth and death rates as well as life
expectancy.
• A population pyramid tells us how many dependants there are. There
are two groups of dependants; young dependants (aged below 15)
and elderly dependants (aged over 65).
• Dependants rely upon the economically active for economic support.
• Many LEDCs have a high number of young dependants, whilst many
MEDCs have a growing number of elderly dependants.

11. Types of population pyramids
1. Expansive population pyramids
• Depict populations that have a larger percentage of people in younger
age groups.
• characterized by their typical ‘pyramid’ shape, which has a broad
base and narrow top.
• Populations with this shape usually have high fertility rates with lower
life expectancies.
• shows a larger percentage of the population in the younger age
cohorts, usually with each age cohort smaller in size than the one
below it.
• The population is said to be fast-growing, and the size of each birth
cohort gets larger than the size of the previous year.
• Many third world countries have expansive population pyramids.

13. 2. Constrictive population pyramids
• Named so because they are constricted at the bottom.
• There is a lower percentage of younger people.
• Describes populations that are elderly and shrinking.
• Often look like beehives and typically have an inverted shape with the graph
tapering in at the bottom.
• Constrictive population pyramids show declining birth rates, since each succeeding age
group is getting smaller and smaller.
• The United States has a constrictive population pyramid.
• The population is generally older on average, as the country has long life expectancy, a
low death rate, but also a low birth rate.
• However, the percentage of younger population are extremely low, this can cause
issues with dependency ratio of the population.
• This pyramid is more common when immigrants are factored out.
• This is a typical pattern for a very developed country, a high level of education, easy
access to and incentive to use birth control, good health care, and few negative
environmental factors.

14. 3. Stationary population pyramids
• Describe populations that are not growing.
• Characterized by their rectangular shape, displaying somewhat equal
percentages across age cohorts that taper off toward the top.
• These pyramids are often characteristic of developed nations, where birth rates
are low and overall quality of life is high.
• There is not a decrease or increase in population; it is stable.
• Austria has a stationary population pyramid.
4. Hour-glass population pyramid
• Symbolizes that the old and the young generations are overrepresented
• The young adult population is comparatively small in size.
• The young adult middle age has been wiped out by certain situations e.g wars,
epidemics (HIV/AIDS), etc,

16. Major Factors affecting Population Structure
• Fertility
• mortality
• Migration
• Other factors are:
– environmental pressures,
– the initial age structure of the population,
– epidemics and other natural disasters, war
• The impact of these events emphasizes the inter-relationships among population change and economic, social,
political, and health factors.
• age and sex differences between populations are significant indicators of health.
• Although it is not shown in population pyramids, an important factor affecting population size is the age at which
individuals become able to reproduce
• A population’s age structure may reveal its health.
• A growing population may have more young individuals than adults at beyond reproductive age.
• A stable population (Type II) often has roughly equal numbers of young members and adults.
• A declining population shows more adults and fewer young (Type III).

17. Factors that affect population change in a country:
1) BIRTH RATE-the number of live births per 1000 in a year
• Birth rates are affected by such factors as nutrition, fertility, attitudes about
abortion, labour value of children, government policies, social value, the
availability of contraception and culture.
2) DEATH RATE-the number of deaths per 1000 in a year
• Death rates are affected by disease, war, medical technology, improved health
care, transportation development and nutrition.
3) IMMIGRATION-the number of people moving into a country.
• Pull factors-characteristics of a place that attracts people to it.
4) EMIGRATION-the number of people leaving a country
• Push Factors-characteristics of a place that causes people to leave.
• Refugees- people who are forced to leave their country due to war, life-
threatening discrimination, famine, or natural disasters.

18. Uses of population pyramid
• Population pyramids can be used to find the number of economic dependents being
supported in a particular population.
• Economic dependents are defined as those under 15 (children who are in full time
education and therefore unable to work) and those over 65 (those who have retired).
• Population pyramids are also useful in planning for the future.
• They can be used in helping to predict changes in the age structure of the population
over the next fifty or so years so that plans can be introduced to cope with the
predicted changes.
• A population pyramid is a tool used in demography to study the changes in population
over time.
• Population pyramids can be used to observe natural increase, birth, and death rate
• Other theories such as the "Youth Bulge" state that when there's a wide bulge around
the 16-30 age range, particularly in males, this leads to social unrest, war and
terrorism.

19. Census
• It is the single largest source of data for population studies all over the world
Total process
• involve enumeration/head count of all the people in a population in a definite
geographic area
• involves collection, collation, analysis, evaluation of information
• Involve publishing and dissemination of the information/data collected
• It produces a snapshot of the population at a point in time
• Demographic, economic and social data are collected
• Characteristics:
• Universality
• Periodicity (every ten years)
• Simultaneity

20. Types:
• de FACTO
• de JURE
de facto
• used in Australia
• Count actual population found on census day wherever they are at the time of
enumeration
• Includes temporary residents and people in transit
• May be bloated if the area has high migration rate
de Jure
• Counts only permanent (habitual) resident population
• Used in USA
• Combined method –
- Used in Brazil and England

21. USES OF CENSUS
•Planning health services
•Determine denominators of indices
of health
•For administrative and political
purpose

22. • HEALTH STATISTICS – these are numerical facts on health services in
general (including vital statistics) and these range from the medical facility
to the demographical and epidemiological information available.
• VITAL STATISTICS – attention here is focused on vital events, the entrance of
an individual into life including all changes in his civil status up to his exit
from life. Vital statistics thus deals with records of birth, illness (morbidity),
marriages/divorces (nuptiality), deaths (mortality).
• Vital Statistics
• These are data on vital events such as births, deaths, marriages, divorces,
separations, annulment and adoption.
• Vital registration system or civil registration system is the continuous
recording of such data

23. SOURCES OF HEALTH AND VITAL STATISTICS
• Census (national)
• Vital Registration systems
• Specific Reporting e.g. Notification of diseases
• Routine abstracts of clinical records – from health institutions
• Special surveys - e.g. epidemiological surveys
• Records of Medical care for specialized groups e.g. armed forces, school health
service, religious organization etc.
• Special methods
• Use of family health visitors as in Igbo-Ora (very expensive)
• Use of religious organizations ad in Kastina
• Collection through selected household heads as in Tanzania
• Collection through a sampling frame as in Turkey

24. USES OF DEMOGRAPHIC DATA
• Planning: for health and other national goals
• Budgetary allocation
• Denominator for calculation of vital rates
• Monitoring and evaluation of health programs
• Allocation of political constituencies
USES OF HEALTH AND VITAL STATISTICS
• Generally, serve as indicators of level of community health which are useful for administrative, research, and planning purposes.
• used for:
• comparison of vital events experienced between two populations
• Comparison of vital events experienced by one population over a given period of time
• Help make decision for preventive action.
• To measure growth of population
• Civil registration is useful because of its value as a legal document
• Uses of Demographic Sample Surveys:
• To update previous complete count
• To check for accuracy of previously collected data
• As source of supplementary data

25. •The end
•Thanks