Demography class notes

1. INTRODUCTION TO STATISTICS
Demography and
vital health statistics
ISUMBA H.L
1/6/2023 5:44:27 AM 1

2. DEMOGRAPHY
• This is the study of the size and
growth of human populations.
• This enables the understanding of
the way the population is
structured.
1/6/2023 5:44:27 AM 2

3. DEMOGRAPHY
• For example, the population of
developed countries is generally
aging while that of the developing
countries is relatively young.
• Using demographic methods, it is
possible to understand how the
population age composition is
changing within age categories and
sex groups.
1/6/2023 5:44:27 AM 3

4. Source of Demographic Data
• Population censuses
• Vital registration
• continuous population
registers
• official records
• Sample surveys.
1/6/2023 5:44:27 AM 4

5. Census
• A census collects data about
the size and composition of
the population at regular
intervals of time, normally 10
years.
1/6/2023 5:44:27 AM 5

6. Census
• In Kenya, the first census was done in
1948. This was followed by another
one in 1962. in 1969, there was the
third census and since that year,
there have been census every 10
years in 1979, 1989, 1999,2009
1/6/2023 5:44:27 AM 6

7. Types of Census
• There are two kinds of
population censuses. These
are:
–De facto census
–De jure census
1/6/2023 5:44:27 AM 7

8. De facto census
•Which involves people
being counted where
they are found on the
night of the census.
1/6/2023 5:44:27 AM 8

9. De jure census
•In which people
are counted
where they
usually live.
1/6/2023 5:44:27 AM 9

10. Vital Registration data
• Vital statistics is the branch of
statistics that deals with data
and the laws of human
mortality, morbidity and
demography.
1/6/2023 5:44:27 AM 10

11. Vital Registration data
• Vital events are births,
marriages and deaths. In Kenya
the registration of vital events,
mainly deaths started in 1904.
• Births were registered from
1906.
1/6/2023 5:44:27 AM 11

12. Vital Registration data
• Registration was exclusive to the
Europeans at that time.
• In 1928, the birth and death
registration act was enacted (Cap
149),registration was extended to
Asians in the same year
1/6/2023 5:44:27 AM 12

13. Vital Registration data
• Africans were included from 1963 but
mainly confined to Nairobi and Nyeri.
The registration of births and deaths in
the rest of the districts was extended in
stages and covered the whole country in
1971.
• Currently failure to register births or
death is punishable according to the laws
of Kenya.
1/6/2023 5:44:27 AM 13

14. Continuous Population Register
• This involves the continuous
updating of records of every
person whenever a
demographic event occurs.
This method is used in
Scandinavian countries.
1/6/2023 5:44:27 AM 14

15. Sample Surveys
• Sample surveys enable the
collection of data from a small
portion of the population to
make inferences on various
parameters of the population on
its basis.
1/6/2023 5:44:27 AM 15

16. Sample Surveys
•Sample survey data is
usually selected
scientifically such that data
collected is representative
of the population.
1/6/2023 5:44:27 AM 16

17. Sample Surveys
Among the major sample surveys
undertaken include:
• The Kenya Demographic surveys
• World Fertility surveys
• The contraceptive prevalence
surveys.
• HIV/AIDS prevalence survey
1/6/2023 5:44:27 AM 17

18. POPULATION CHANGE
The population is affected by three
things:
•Births
•Death
•Migration
1/6/2023 5:44:27 AM 18

19. POPULATION CHANGE
• Birth and in-migration increase the
size of the population.
• Death and out-migration decrease
the size of the population.
• These factors can also affect age-sex
structure.
1/6/2023 5:44:27 AM 19

20. POPULATION CHANGE
• The number of births can be
estimated from birth rate.
• The birth rate is an event type-rate.
The time period for counting events
must be stated. Usually, this time
period is one year.
1/6/2023 5:44:27 AM 20

21. Measurement of Age
• Age is an important variable in
demographic analysis. It provides the
basic criteria for classification in vital
statistics, censuses and surveys.
• Most of the demographic data is
expressed in terms of age at which an
event occurs e.g. the time an individual
leaves school, enters employment or
dies.
1/6/2023 5:44:27 AM 21

22. Age Structure.
• Less developed countries tend to
have high fertility; high mortality and
young population while more
developed countries have low
fertility, low mortality and old
populations.
1/6/2023 5:44:27 AM 22

23. Age Structure.
• As a country develops, it goes
through demographic transition.
Transition simply means going from
high fertility and high mortality to
low fertility and low mortality
regimes.
1/6/2023 5:44:27 AM 23

24. Types of population pyramids
Population pyramids for 4 stages of the
demographic transition model
• While all countries' population pyramids
differ, four general types have been identified
by the fertility and mortality rates of a
country.
1. Stable pyramid
• A population pyramid showing an unchanging
pattern of fertility and mortality..
1/6/2023 5:44:27 AM 24

25. Types of population pyramids
2. Stationary pyramid
• A population pyramid typical of countries with
low fertility and low mortality, very similar to a
constrictive pyramid.
3. Expansive pyramid
• A population pyramid that is very wide at the
base, indicating high birth and death rates.
1/6/2023 5:44:27 AM 25

26. Types of population pyramids
4. Constrictive pyramid
• A population pyramid that comes in at the
bottom. The population is generally older on
average, as the country has long life
expectancy, a low death rate, but also a low
birth rate. Common when immigrants are
factored out, especially in developed country,
where there is a high level of education, easy
access to and incentive to use birth control,
good health care, and few negative
environmental factors.
1/6/2023 5:44:27 AM 26

27. Demographic transition model
1/6/2023 5:44:27 AM 27

28. Methods of Measuring Age in Africa
•Historical calendar
method.
•Cohort identification
method.
1/6/2023 5:44:27 AM 28

29. Historical calendar method.
• In this method, the interview takes the
respondent through a list of historical
events in order to identify the events
the respondent recalls.
• These events are usually based on a
calendar of events of natural
significance, which help to place the life
events of individuals on a time scale.
1/6/2023 5:44:27 AM 29

30. Cohort identification method.
• This involves the identification of age
cohorts in the population, linking the age
cohorts to the standard time scale. E.g.
using the date of circumcision where all
those circumcised in the same year are
considered to belong to the same group,
each group being given the same name.
• These groups form cohorts from which age
data can be obtained.
1/6/2023 5:44:27 AM 30

31. Causes of Errors in age data.
• Ignorance of correct age
• Carelessness in reporting and
recording
• A general tendency to state figures
ending in certain preferred digits
1/6/2023 5:44:27 AM 31

32. Causes of Errors in age data.
• A tendency to exaggerated length of
life at advanced ages.
• A possible subconscious aversion of
some numbers
• Miss-statement arising from motives
of an economic, social, political or
purely personal character.
1/6/2023 5:44:27 AM 32

33. Population Composition by Sex and age Structure.
• A normal age structure from an
accurate census data follows a typical
pattern.
• It starts with a large number (or
proportion) in the youngest age group
(0 – 4) for each sex.
• It gradually diminishes in subsequent
age groups until age group at about 100
years at which the number becomes
very small or nil.
1/6/2023 5:44:27 AM 33

34. Population Composition by Sex and age
Structure.
• Between the sexes; males
predominate the first few
quinquinnial ages groups and then
falls below the numbers of females.
• The difference gradually widens at
advanced ages.
1/6/2023 5:44:27 AM 34

35. A population pyramid
• Also called an age pyramid or age picture
diagram, is a graphical illustration that shows
the distribution of various age groups in a
population (of a country or region of the
world), which forms the shape of a pyramid
when the population is growing.
• It is also used in ecology to determine the
overall age distribution of a population; an
indication of the reproductive capabilities and
likelihood of the continuation of a species.
1/6/2023 5:44:27 AM 35

36. A population pyramid
• It typically consists of two back-to-back bar
graphs, with the population plotted on the X-
axis and age on the Y-axis, one showing the
number of males and one showing females in
a particular population in five-year age groups
(also called cohorts).
• Males are conventionally shown on the left
and females on the right, and they may be
measured by raw number or as a percentage
of the total population.
1/6/2023 5:44:27 AM 36

37. A population pyramid
• Population pyramids are the most effective
way to graphically depict the age and sex
distribution of a population, due to clear
image the pyramids present.
• A population pyramid also tells how many
people of each age range live in the area.
• There tends to be more females than males in
the older age groups, due to females' longer
life expectancy.
1/6/2023 5:44:27 AM 37

38. 1/6/2023 5:44:27 AM 38
Population pyramid

39. Population pyramids
The rectangle (bar) representing an
age, or group of ages, has length that
depends on:-
• The total at births of the
corresponding cohort
• The amount of reduction by
mortality
• The amount of migration.
1/6/2023 5:44:27 AM 39

40. Population Distribution and Density
• Refers to how many people live in a
given area of land.
• To calculate the population density,
you divide the number of people by
the available land area (in square
kilometres).
• Population density may be high or
low
1/6/2023 5:44:27 AM 40

41. VITAL HEALTH STATISTICS.
•These are statistics which
relate to births, death and
health status of the people.
1/6/2023 5:44:27 AM 41

42. SOURCES OF VITAL HEALTH DATA.
• Registers of vital events.
E.g. births, deaths, marriage,
migrations etc.
• Population census:
• This is important sources on
economic, social, demographic
information.
1/6/2023 5:44:27 AM 42

43. SOURCES OF VITAL HEALTH DATA.
• Surveys: Provide timely data
on relevant topics of interest.
• Routine health services data.
• Patients records; monthly
reports
1/6/2023 5:44:27 AM 43

44. Rates obtained from vital data
•Fertility rates
•Morbidity rates
•Mortality rates.
1/6/2023 5:44:27 AM 44

45. FERTILITY MEASURES.
• Fertility refers to the actual
reproductive performance of a
population.
• Or
• It is the number of live births
occurring in a population.
1/6/2023 5:44:27 AM 45

46. Factors Affecting Fertility.
• Age at marriage or cohabitation,
• Availability and use of family planning,
• Economic development,
• Status of women
• Age-sex structure.
Time limitations of fertility rate are mostly
one year; mostly referred to as
periodical fertility.
1/6/2023 5:44:27 AM 46

47. BIRTH RATE.
• Birth rate (also called crude birth rate-
CBR) indicates the number of live births
per 1000 population in a given year
• It is crude because everybody is
included.
• The CBR measures the fertility
experience of all ages of the population.
• It measures the contribution of current
fertility to overall population growth.
1/6/2023 5:44:27 AM 47

48. BIRTH RATE.
CBR = No. of births in a year X 1000
Total population in which those
births have occurred.
• CBR is affected by compositional factors,
which include age, sex, and marital status.
1/6/2023 5:44:27 AM 48

49. GENERAL FERTILITY RATE (GFR)
• The general fertility rate (also called
fertility rate) is the number of live
births per 1,000 women aged 15 - 44
(9) years in a given year.
• No. of births in a year x 1,000 = GFR.
No of women aged
15 - 44 (9) years
1/6/2023 5:44:27 AM 49

50. GENERAL FERTILITY RATE (GFR)
• The general fertility rate is more
refined measure than the CBR
because it relates births more nearly
to the age - sex group at risk of giving
births (women 15 - 44 years of age).
• Thus GFR is much more indicative
of changes in fertility behavior than
is the
1/6/2023 5:44:27 AM 50

51. AGE SPECIFIC FERTILITY RATE (ASFR)
• Fertility rates can also be
obtained for specific age groups
for comparison over time or to
see differences in fertility
behaviour at different ages.
1/6/2023 5:44:27 AM 51

52. AGE SPECIFIC FERTILITY RATE (ASFR)
No. of births in specified age
(age group) in a year.) X 1,000 = ASFR.
No. of women of the specified age
(age group)
1/6/2023 5:44:27 AM 52

53. AGE SPECIFIC FERTILITY RATE (ASFR)
Uses of ASFR:
(1)as a measure of the age pattern of
fertility, that is of the relative frequency
of childbearing among women of
different ages within the reproductive
years,
(2) as an intermediate computation in the
derivation of the total fertility rate
(TFR).
1/6/2023 5:44:27 AM 53

54. MORBIDITY MEASURES.
• Morbidity pertains to the ratio of the
sick/ill health to the well persons in a
community at a specified period of
time.
OR
• Morbidity refers to disease and illness in
a population.
• Measures are: Incidence rate and
Prevalence rate
1/6/2023 5:44:27 AM 54

55. MORTALITY MEASURES.
• Mortality refers to deaths as
a component of population
change.
• Is the proportion of
population who die due to a
disease or any other causes.
1/6/2023 5:44:27 AM 55

56. MORTALITY MEASURES.
• The measures are:
Death rate
Age specific mortality
Maternal mortality
Infant mortality
Still births etc
1/6/2023 5:44:27 AM 56

57. DEATH RATE.
• The death rate (also called crude
death rate) is the number of deaths
per 1,000 population in a given year.
No of deaths x 1000 = CDR
Total population
• Crude because everybody is
included.
1/6/2023 5:44:27 AM 57

58. AGE SPECIFIC DEATH RATE.
• Deaths occurring to specific age group and can
be used for comparison of mortality at
different ages or a change in mortality at the
same age over time.
No of deaths occurring in a specified age
(age group) at a specified time x 1000 = ASDR
Total population of the specified age (age
group).
1/6/2023 5:44:27 AM 58

59. INFANT MORTALITY RATE (IMR)
• Is the number of deaths to infants under one
year of age per 1,000 live births in a given
year.
• No.of death of infants
under one year of age X 1,000 = IMR
Total live births in the same period.
• A year measure of deaths rate of children
especially less than one year old.
• It is usually used as a measure of health status
in a community
1/6/2023 5:44:27 AM 59

60. MATERNAL MORTALITY RATE.
• Is the number of women who die as a result of
child-bearing in a given year per 100,000
births in that year. Maternal deaths are those
caused by complications of pregnancy and
childbirth.
• No of maternal deaths X 100,000 MMR.
• Total live births
• Used to assess mother/child health care level
1/6/2023 5:44:27 AM 60

61. STILLBIRTH RATE (SBR).
• No of stillbirths in a
period of time X 1,000 SBR
Total live and stillbirths during the same
period of time.
• Used to assess ANC care and delivery
system in labour ward.
1/6/2023 5:44:27 AM 61

62. END
1/6/2023 5:44:27 AM 62