1. Dr Paul T Francis, MD Prof. Com Med College of Medicine, Zawia
Demography 1
Dr Paul T Francis, MD
Prof. Com Med
College of Medicine, Zawia

2. Demography Demography is the scientific study of human population
Demography studies 3 aspects of a population
Changes in population size
Composition of population
Distribution of population in place

3. Demographic processes
The demographic processes that determine the size, composition and distribution of a population are:
Fertility
Mortality
Marriage
Migration
Social mobility

4. Sources of Demographic information
Population census
Vital statistics
Migration
Before we plan any health intervention or programmes for the community we should know the size and composition of the community
We also need to know the changes that will occur to the size and composition to the population

5. Demographic cycle
Population of all countries go through the following stages
1st stage – High stationary
2nd stage – Early expanding
3rd stage – Late expanding
4th stage – Low stationary
5th stage – Declining

6. Demographic cycle High stationary
There is high birth rate and high death rate so the population remains stationary.
There is no increase or decrease in the population

7. Demographic cycle Early expanding
Death rate begins to decline while birth rate does not change
Many countries in Asia and Africa are in this stage

8. Demographic cycle Late expanding
The death rate declines further and the birth rate also starts to decline.
Since the death rate is lower than birth rate the population keeps increasing
Some developing countries are in this stage
Libya is in this stage

9. Demographic cycle Low stationary
In this stage the death rate and the birth rate are both low
So the population becomes stationary again
There is no increase or decrease in the population

10. Demographic cycle Declining
In this stage the birth rate is lower than the death rate
So the population starts to decline

12. World population
Total population of the world about 2000 years ago was 250 million
In 1800 the world population became 1000 million (1 billion)
In 1987 the world population became 5 billion
In 1999 the world population became 6 billion
Expected to become 8 billion by 2025

13. World population
About ¾th of world population lives in the developing countries
China and India are the two most populous countries in the world
The world population growth rate was at the peak in 1970
About 95% of the population growth is occurring in the developing countries

14. Life expectancy
Life expectancy is the average number of years which a person of a particular age may expect to live
It is one of the best indicators of a country’s level of development and overall health status
The life expectancy of people all over the world has been increasing

15. Life expectancy at birth
In most countries the life expectancy of women is more than that of men
Life expectancy in Japan is the highest ♀ 86 ♂79
Life expectancy in USA is ♀ 80 ♂76
Life expectancy in Libya is
♀75 ♂70

16. Fertility Fertility – Is the actual bearing of children by a woman
The reproductive age of a woman is between 15 – 45 years
Some factors affecting fertility are:
Age at marriage
Duration of married life
Spacing of children
Education
Socioeconomic status

17. Estimated mid-year population
Fertility
Birth rate =
Growth rate =
Crude birth rate – Crude death rate
Number of live births during the year
Estimated mid-year population
X 1000

18. Demographic indicators of Libya
Crude Birth rate (1978) = 47.0
Crude Death rate (1978) = 5.1
Growth rate is 42/1000 = 4.2%
Total fertility rate (per woman) = 2.8

19. Population structure of Libya
< 5 = 20.7%
<15 = 51.4%
<20 = 59.6%
Sex ratio of Libya is 940 women for 1000 men
Urban population 60% and rural 40% of total population

20. Summary
Study of population is important for promoting health of population
The size and composition of the population will help us plan for health interventions
Study of human population will help us plan for the future health needs of a community.