2. Outline
Definition of demography
Births, Deaths, Migration Rates and Patterns,
Functions of Fertility, Mortality and Population.
Social and Economic Factors Interplay in Future
Demographic Trends, World Trends, African Trends,
and Kenyan Trends
Population Pyramid, Sources of Demographic Data,
Vital Health Statistics; importance, sources, types,
utilization
3. Definition
Demography is the scientific study of human populations
primarily with respect to their size, their structure
{composition} and their development {change}
Demography can be defined as the quantitative study of
five demographic processes –
Fertility (births)
Mortality (deaths)
marriage
Migration (population movements)
social mobility (change in status or circumstances). –
these five process determine the size, composition, and
distribution of the population
4. DEMOGRAPHY…
Composition of population --- ethnic, age, sex
(also, how many are non-citizens)
Distribution --- % rural, % urban, % suburban.
Also, how many citizens live overseas
Growth --- rapid growth, slow growth,
population decline
5. DEMOGRAPHY…
Population is affected by fertility, mortality
and migration rates
Final population = Initial population + (Births –
Deaths) + (Immigration – Emigration)
8. 1. Fertility (Births)
Actual reproductive performance (behavior) of a
woman/ couple
Generally confined to women
Fecundity - physical ability to reproduce
Fertility - the actual production of offspring
Crude Birth Rate - number of births per year per
thousand people
Total fertility rate - number of children born to an
average woman during her reproductive life
Zero population growth (ZPG) - occurs when births
+ immigration just equal deaths + emigration
9. Crude Birth Rate (CBR)
Crude birth rate indicates the number of live
births occurring during the year, per 1,000
population estimated at midyear
CBR = Number of live births in a year X 1000
Total mid-year population
10. Fertility rates can be affected by:
Public policy e.g. some governments pressure
couples to have fewer kids, other governments
encourage them to have more!
Culture e.g. religion and contraception
Economics e.g. expense of having kids in industrial
versus agricultural societies
Technology e.g. are effective contraceptive
methods available?
11. FERTILITY AND HEALTH
High fertility can increase maternal and child
mortality
Continuous child-bearing can have a negative
impact on maternal health
Closely-spaced births (<18 months apart) & low
birth weight babies (<2,500g) at higher risk
Illegal abortions and maternal mortality
“Female genital mutilation” & maternal mortality
Sex-selective abortion in China and India
12. General Fertility Rate (GFR)
• The GFR is the number of live births per 1000
females aged 15-49 years (fertile age group) in a
given year.
• The GFR is approximately four times the CBR.
• GFR = Number of live births in a year X 1000
Number of females 15-49 years of age
13. Age specific fertility rates (ASFR)
• The ASFR is defined as the number of children
born alive to females in a specific age group
per 1000 females in that specific age group.
Exercise:
If there were 2,000,000 women in the age group 15-19 years and
if there were 100,000 live births to women in the same age group,
calculate the age specific fertility rate
14. Total Fertility Rate (TFR):
The TFR is the average number of children that would be
born to a woman throughout her life time or her child
bearing age (15-49 years), if she were to pass through all
her child bearing years at the same rates as the women
now in each age group.
TFR sums up in a single number the Age Specific Fertility
Rates of all women at a given point in time.
If 5 – year age groups are used, the sum of the rates is
multiplied by 5.
This measure gives the approximate magnitude of
“completed family size”.
TFR = (Sum of all Age specific fertility rates) x age interval
(usually 5).
15. Gross Reproduction Rate (GRR):
The GRR is the average number of daughters that
would be born to a woman throughout her
lifetime or child bearing age (15-49 years), if she
were to pass through all her child bearing age.
This rate is like the TFR except that it counts only
daughters and literally measures “reproduction”; a
woman reproducing herself by having a daughter.
The GRR is calculated by multiplying the TFR by
the proportion of female births (sex ratio at birth).
GRR = (TFR x female births)/(Male + Female
births)
16. FERTILITY AND HEALTH…
Problem of teenage pregnancies
STDs such as gonorrhea can lead to infertility
in women
Use of condoms reduce transmission of STDS
e.g. HIV/AIDS
Monogamous women at risk of being infected
with HIV by husbands and boyfriends
17. 2) MORBIDITY AND MORTALITY
These refers to diseases and deaths in a
population
Measures of morbidity includes:
Incidences
Prevalence
Measures of mortalities includes;-
Under 5 mortality rate
Life expectancy at birth
Age-specific mortality rates
Cause-specific mortality rates
Maternal mortality rate
18. Crude Death Rate (CDR)
• Crude death rate = deaths per 1000 people in
population per year
19. 3. migration
Internal migration: within a country e.g. rural to
urban
International migration: skilled professionals to
other countries
Reasons?
Involuntary: slavery, ethnic persecution, wars,
natural disasters, famines
Voluntary: to seek jobs (skilled or unskilled), to get
an education, because of marriage, upon
retirement
20. MIGRATION AND HEALTH
Migrants (workers, prostitutes, truck drivers)
may spread infectious diseases e.g. HIV/AIDS,
TB, diphtheria
Jet travel speeds up disease transmission
Migrants often live in urban slums and
experience adjustment problems (these can
affect their physical or mental health)
21. Population growth
The population of the world is growing at an
exponential rate, faster and faster
Population growth rate is influenced by:
Birth
Death
Immigration
Emmigration
Current estimated world population >7.8 B
22. Population growth rates…
A population with a growth rate of 1% per annum will
double in size every 70 years.
A population with a growth rate of 2% per annum will
double in size every 35 years.
A population with a growth rate of 3% per annum will
double in size every 23 years.
Thus, a growth rate of two or three percent can have
huge consequences for a population in a short period of
time.
When the birth rate is higher than the death rate, the
population grows, this is called natural increase
When death rates are higher than birth rate, the
population decreases, this is called natural decrease
23. Population Structure (Composition)
Population structure refers to the composition of the
population in terms of :
age
sex
occupation
religion
educational status
geographical distribution
socio– economic status etc.
the structure of a population is influenced by
fertility
mortality
migration
24. Population pyramid
The most important demographic characteristic of a
population is its age-sex structure
This is displayed in population pyramids
Age-sex pyramids display the percentage or actual
number of a population broken down by gender and age.
The five-year age increments on the y-axis allow the
pyramid to vividly reflect long term trends in the birth
and death rates but also reflect shorter term baby-
booms, wars, and epidemics.
By convention:
males are shown on the left and females on the right of the
pyramid.
Young persons are at the bottom and the elderly at the top.
26. 1. Rapid Growth Pyramid
triangle-shaped pyramid ( broad base and
narrow top)
reflects a high growth rate.
It indicates a high percentage of young
population and rapid population growth.
The low survivorship and high natality of
human population in many developing
countries result in a pyramidal stable age -
structure, in which most of the population is
young.
28. 2. Slow Growth Pyramid ( constrictive)
used to describe populations that are elderly
and shrinking
typically have an inverted shape with the
graph tapering in at the bottom
smaller percentages of people are in the
younger age cohorts
characteristic of countries with higher levels of
social and economic development, where
access to quality education and health care is
available to a large portion of the population
30. 3.Negative Growth Pyramid ( stationary)
Stationary, or near stationary, population
pyramids are used to 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.
32. Diversity in trends
When discussing global population trends and
growth rates, the large diversity between
countries and regions is obscured.
While the global population is still growing,
this growth is concentrated in certain regions,
while other regions experience very low
growth rates or even decline.
35. Sub-Saharan Africa 2019 PGR 2.7
Rwanda 2.6
Sao Tome and
Principe
1.9
Senegal 2.7
Seychelles 0.9
Sierra Leone 2.1
Somalia 2.9
South Africa 1.3
South Sudan 0.8
Sudan 2.4
Tanzania 3.0
Togo 2.4
Uganda 3.6
Zambia 2.9
Zimbabwe 1.4
Guinea 2.8
Guinea-Bissau 2.5
Kenya 2.3
Lesotho 0.8
Liberia 2.4
Madagascar 2.7
Malawi 2.6
Mali 3.0
Mauritania 2.7
Mauritius 0.0
Mozambique 2.9
Namibia 1.9
Niger 3.8
Nigeria 2.6
36. Consequences of rapid population growth and high fertility
Pressure on public services and infrastructure
Potential food shortages
Environmental degradation
Reduced economic growth
Maternal mortality and morbidity
Climate change
37. The Demographic Transition
A fundamental model developed to describe
population dynamics is the Demographic
Transition model.
The model proposes four stages in the evolution
of the population in a society:
1. Stage 1(High fertility, high mortality)
2. Stage 2 (High fertility, declining mortality)
3. Stage 3 (Declining fertility, low mortality)
4. Stage 4 (Low fertility, low mortality)
38. 1. Stage 1(High fertility, high mortality)
this depicts agrarian civilizations (pre-industrial
stage)
characterized by:
stable or slowly growing populations with crude
birth rates greater than 45 per 1000
crude death rates greater than 35 per 1000 births.
Agricultural existence favours large families.
However high birth rates are balanced by high
death rates from diseases famine, war etc
resulting in very low population growth.
39. 2. Stage 2 (High fertility, declining mortality):
this depicts the industrializing nations.
Advances in sanitation and improved availability
and quality of food, water, and shelter lead to fall
in death rate and an increase in life expectancy.
This has usually occurred without an immediate
change in birth rate; however, the improved
conditions of life may favour an increase in
fertility.
During this period, a marked excess of births over
deaths develops leading to a rapid expansion of
population
40. 3. Stage 3 (Declining fertility, low mortality):
Characterized by falling growth Rates.
After a time, birth rates tend to fall, largely as a reflection
of industrialization and consequent urbanization.
With industrialization people tend to migrate from rural
to urban areas, which favours small families
There is a greater geographic proximity to health care
service and to the availability of information and service
for disease and family planning.
These various factors increase the likelihood that
contraceptive practices, and even abortion, will be
adopted.
41. 4. Stage 4 (Low fertility, low mortality)
this is a stage of stable population.
This stage is reached in highly developed
societies when both birth and death rates are
low and population growth rates are zero or
even negative.
