7/11/2009 1Dr. Salwa Tayel

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Family and Community Medicine DepartmentFamily and Community Medicine DepartmentKing Saud UniversityKing Saud University

DEMOGRAPHYDEMOGRAPHY

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Learning objectives Learning objectives

1.1. Calculate rates measuring the growth of the Calculate rates measuring the growth of the

populationpopulation

2.2. Determine population doubling time.Determine population doubling time.

3.3. Know the Concept of Demographic transitionKnow the Concept of Demographic transition

4.4. List The stages of demographic transitionList The stages of demographic transition

5.5. List factors affecting Population DynamicsList factors affecting Population Dynamics

By the end of this lecture you will be able to:By the end of this lecture you will be able to:

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Rates measuring the growth of Rates measuring the growth of the populationthe population

1.1. Rate Of Natural IncreaseRate Of Natural Increase

The natural increase in size of any population is the The natural increase in size of any population is the

product of subtraction of deaths from births.product of subtraction of deaths from births.

Rate of natural increase (RNI) =Rate of natural increase (RNI) =

100..

XyearandlocalitysameofpopulationyearmidEstimated

yearandlocalityaindeathsofNobirthsofNoRNI

10

ratedeathCruderatebirthCrudeRNI

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ExampleExample

In KSA in 2004In KSA in 2004

Crude Birth Rate:Crude Birth Rate: 25.3/1000 population 25.3/1000 population

Crude Death Rate: 3.8/1000 populationCrude Death Rate: 3.8/1000 population

Calculate RNI?Calculate RNI?

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2.2. Growth rateGrowth rate

The growth rate takes into consideration not The growth rate takes into consideration not

only births and deaths but also migration.only births and deaths but also migration.

Growth rate (GR) = RNI + Net migration rateGrowth rate (GR) = RNI + Net migration rate

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• If a population is growing at a constant rate of 1% per year If a population is growing at a constant rate of 1% per year

it would be expected to double in 69.3 years it would be expected to double in 69.3 years

(approximately every 70 years). A Law of 70 is much (approximately every 70 years). A Law of 70 is much

simpler to remember than a Law of 69.3 simpler to remember than a Law of 69.3

• If the rate of growth is 2% then the expected doubling time If the rate of growth is 2% then the expected doubling time

is 70/2 or 35 years.is 70/2 or 35 years.

Population Doubling timePopulation Doubling time

Law of 70Law of 70

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The demographic transition is the description of The demographic transition is the description of

secularsecular trends in population growth in relation to trends in population growth in relation to

changes over time in death or changes over time in death or mortalitymortality rates rates

and birth or and birth or fertilityfertility rates. rates.

Demographic transition describes the major Demographic transition describes the major

demographic trends that happened to Western demographic trends that happened to Western

countries in the past two centuries.countries in the past two centuries.

Demographic transition

7/11/2009 Dr. Salwa Tayel 9Source: Joseph A. McFalls, Jr. Population: A Lively Introduction. Third edition. Population Bulletin 53(3); 1998: 39.

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The stages of the demographic transitionThe stages of the demographic transition

During stage 1, both the death rate and the birth rate are high. During stage 1, both the death rate and the birth rate are high.

The birth rate is constant, while the death rate fluctuates in The birth rate is constant, while the death rate fluctuates in

the face of natural disasters as famines, floods, epidemics, the face of natural disasters as famines, floods, epidemics,

and wars. and wars.

There are many reasons for this:There are many reasons for this:

many children die in infancy (high infant mortality), so parents many children die in infancy (high infant mortality), so parents

tend to have more children to compensate for deathstend to have more children to compensate for deaths

children are needed to work on the land to grow food and for children are needed to work on the land to grow food and for

family supportfamily support

high death rates because of epidemics, famines, poor diet, high death rates because of epidemics, famines, poor diet,

poor hygiene and little medical care. poor hygiene and little medical care.

Stage 1 (high stationary)Stage 1 (high stationary)

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Stage (1) High stationary:Stage (1) High stationary: High birth rate and high death rateHigh birth rate and high death rate

High High stationarystationary e.g. central Africa e.g. central Africa

(Slow population growth)(Slow population growth)

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Stage 2 (early expanding)Stage 2 (early expanding)During stage 2, Birth rate remains high but the death rate begins a During stage 2, Birth rate remains high but the death rate begins a

sharp decline due to major improvements in living standards sharp decline due to major improvements in living standards attributable to industrialization. attributable to industrialization.

The large gap between the birth rate and the death rate accounts The large gap between the birth rate and the death rate accounts for the population explosion.for the population explosion.

The reasons for declining death rate are:The reasons for declining death rate are: Improvements in sanitation and water supplyImprovements in sanitation and water supply Better quality and quantity of food producedBetter quality and quantity of food produced Transport and communications improve the movements of food Transport and communications improve the movements of food

and medical suppliesand medical supplies

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Stage (2) Early expanding: Stage (2) Early expanding:

High birth rate and rapid fall of death rate.High birth rate and rapid fall of death rate.

Rapid population growthRapid population growth

(Population explosion)(Population explosion) e.g. India. e.g. India.

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Stage 3 (late expanding)Stage 3 (late expanding) During stage 3, Birth rates fall rapidly as people start controlling

their fertility and limiting family size.

The fall in birth rate is due to:

Lower infant mortality rate so, most of the children will actually

survive into adulthood

Children become more expensive to raise largely because of

increasing educational demands.

A declining need for children as farm labors due to

industrialization and mechanization

Increased access to contraception

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Stage (3) Stage (3) Late expanding: Late expanding:

High fall of birth rate and rapid fall of death rate.High fall of birth rate and rapid fall of death rate.

Moderate population growthModerate population growth e.g. Egypt. e.g. Egypt.

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Stage 4 (low stationary)Stage 4 (low stationary)

In stage 4, the final stage, both birth rates In stage 4, the final stage, both birth rates

and death rates are low. But in contrast to and death rates are low. But in contrast to

stage 1, birth rates fluctuate, indicative of stage 1, birth rates fluctuate, indicative of

fertility control as people alter their fertility control as people alter their

reproduction according to socioeconomic reproduction according to socioeconomic

changes.changes.

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Stage (4) Low stationary: Stage (4) Low stationary:

Low birth rate and low death rate.Low birth rate and low death rate.

e.g. most industrialized countriese.g. most industrialized countries

(Slow population growth)(Slow population growth)

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United States Population, 1995United States Population, 1995

Source: Joseph A. McFalls, Jr. Population: A Lively Introduction. Population Bulletin 46(2); 1995: 22.

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Source: Joseph A. McFalls, Jr. Population: A Lively Introduction. Population Bulletin 46(2); 1995: 22.

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Stage 5 (declining)Stage 5 (declining)

A new fifth stage is added to the model, A new fifth stage is added to the model,

due to some countries such as Germany, due to some countries such as Germany,

Japan,.. having higher death rate than Japan,.. having higher death rate than

birth rate, so that their populations are birth rate, so that their populations are

actually falling.actually falling.

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Stage (5) Declining: Stage (5) Declining:

Death rate > birth rateDeath rate > birth rate

DeclineDecline e.g. Japan e.g. Japan

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Population DynamicsPopulation Dynamics Population dynamics include the complex Population dynamics include the complex

interaction of the components of population interaction of the components of population

growth, their determinants and consequences.growth, their determinants and consequences.

The components of population dynamics areThe components of population dynamics are

Fertility.Fertility.

Mortality.Mortality.

Migration.Migration.

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1000)(

XalityyearandlocsamepopulationmidyearEstimated

localityandyearcertainainbirthsliveofnumberTotalCBR

=… Live Births/ 1000 population in a year.

1.1. Crude Birth Rate (CBR)Crude Birth Rate (CBR)

Is the simplest Is the simplest indicatorindicator of fertility. of fertility.

It is defined as the number of live births per 1000 It is defined as the number of live births per 1000

mid-year population in a given year and locality.mid-year population in a given year and locality.

I - Fertility (Natality Rates)I - Fertility (Natality Rates)

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2.2. General fertility rate (GFR)General fertility rate (GFR) It relates births to females in the child It relates births to females in the child

bearing period (15-49 years).bearing period (15-49 years).

1000)4915(

Xagedpopulationfemalevereproductiyearmid

localityandyearcertainainbirthliveofnumberTotalGFR

= …Live birth/1000 female population aged 15-49.= …Live birth/1000 female population aged 15-49.

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3. Age specific fertility rate =

1000XTotal

group age specific samethe in population Female

locality and year certain a in group age specifica in femalesby born births live of number

= …Live births/1000 female population in specified age group.

It is the most sensitive indicator of fertility

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ExampleAge specific fertility rate in (15-19) age group =

1000locality andyear same in the group age 19)-(15 in the population Female

locality andyear certain ain group age 19)-(15in femalesby born births live ofnumber X

Total

= …Live births/1000 female population in 15-19 year group.

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4 - Total fertility rate (TFR):4 - Total fertility rate (TFR):

TFR represents the number of births that would be born to a woman throughout her reproductive period.

• In developing countries the TFR is over 6.0 children per woman, a very high rate.

•In most developed countries the TFR is under 2.0.

•TFR in Egypt in year 2000 was 3.4 children/woman.

•TFR in KSA in year 2004 was 3.68 children/woman