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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.