Principles of Demography.pdf

Principles of DemographyPrinciples of Demography

Department of Family & Community MedicineEmilio Aguinaldo College of Medicine

Session ObjectivesSession Objectives

Describe the elements of demography Describe populations as to:

− Size− Composition/structure− Distribution

Describe factors affecting population kinetics

AT THE END OF THE SESSIONAT THE END OF THE SESSION

1. Describe the elements of demography2. Describe populations as to:

SizeComposition/structureDistribution

3. Describe factors affecting population kinetics

DEMOGRAPHYDEMOGRAPHY

The science of populations Derived from the Greek words

“snyos”- people“ypagly”- to draw or write

The natural and social history of human species or the mathematical knowledge of populations, of their general changes and of their physical, civil , intellectual, moral conditions

(Achille Gillard, 1855)

DEMOGRAPHYDEMOGRAPHY

The empirical, statistical and mathematical study of human populations

(Bogue)

“Population dynamics” which deals with population size, composition, distribution and behavior

FOCI OF DEMOGRAPHYFOCI OF DEMOGRAPHY

Size

Distribution

Composition


Size Population changes Population dynamics Population kinetics

Natality Mortality Migration


Measurable characteristics of people

Sex Age Marital Status Education Occupation

Composition


How are people distributed?

Village Town Province...

Distribution

PUBLIC HEALTH APPLICATIONSPUBLIC HEALTH APPLICATIONS

Prevention and control of public health problems

how large is the population affected and where they are found

population growth and dispersal to predict future developments and consequences

SOURCES OF SOURCES OF DEMOGRAPHIC DATADEMOGRAPHIC DATA

Most common sources of information1) Censuses 2) Sample surveys3) Registration systems

Other sources: population registers voter’s registry school rosters

CENSUSCENSUS

The total process of collecting, compiling and publishing demographic data, economic and social data, pertaining at a specified time or times, to all persons in a country or delimited territory

Most nations once every 10 years

CENSUSCENSUS

Examples

First census March 2002 and the last in 2012The reference point in time for the last census was 00 hours on March 1, 2012.

The first day of March is chosen as the reference day because on this day, most of the people are found in their hometowns.

CENSUSCENSUS

Minimum list of information collected: Age, sex, race or ethnicity No. of children ever born by married women Literacy or educational attainment Marital status Place of birth Occupation

CENSUSCENSUS

Defined as the simultaneous recording of demographic , social and economic data of individuals of a country on a specified day Data are compiled, analyzed and published. Demographic data include age, sex, place of birth, literacy and technical, post-graduate qualifications

CENSUSCENSUS

Social data include religion, native language, type of house, energy-fuel used.

Economic data – income, occupation, subsidiary occupation (s), home enterprise, etc.

CENSUSCENSUS

May includeHouse occupant status (landlord/tenant)Chief material used in the construction of

floor/wall/roofNumber of rooms and average members per

roomAvailability of bathroom and toilet inside the

houseNumber of persons per toiletSource of water supply

CENSUSCENSUS

May includeSource of electricitySource of light and alternative sourcesType of fuel used for cookingDistance of workplace from homeMode of transportation to workplaceAvailability of telephone, refrigerator and other

appliancesUse of bank accounts for financial dealings

CENSUSCENSUS

May includeNumber of married couplesDate of marriage of the married couplesNumber of children ever born to the married

couplesBirth of a child in the past year

Other dataHandicapped persons, disabilities such as

visual, auditory, speech, musculoskeletal, mental

STEPS IN DOING THE CENSUSSTEPS IN DOING THE CENSUS

1) Identify the target population

2) Identify the territorial domain of this population, its location and accessibility by the surveyors

3) Determine how the are is divided (e.g. by regions, by districts, by barangays)

4) Identify if previous house numbers were assigned to a specific household.

STEPS IN DOING THE CENSUSSTEPS IN DOING THE CENSUS

5) Collect information about the housing condition, and quality of life of the inhabitants

6) Collect the necessary demographic data, social, economic and disability data 7) Inquire whether anyone was born/died from the date of the previous visit up to the day the census is made. If yes, was this data placed in the previously collected data?

USES OF THE CENSUSUSES OF THE CENSUS

Gives the exact size of the population of the country

The difference between two censuses gives one the difference in population and then population growth can be predicted

Gives us the idea of how successful the population control program is

Gives the true picture and composition of the population

USES OF THE CENSUSUSES OF THE CENSUS

Used in the calculation of different health indices

Used in planning various public health programs

Used to assess the quality of life of the people in a given country

2 WAYS OF ALLOCATING 2 WAYS OF ALLOCATING PEOPLE IN A CENSUSPEOPLE IN A CENSUS

1. De facto method – people are allocated to the areas where they were physically present at the census date regardless of where they usually live

2. De jure method – assigns individuals to the place of their usual residence regardless of whether they were actually enumerated during the census

ERRORS IN A CENSUSERRORS IN A CENSUS

Infants are generally under numerated

Many persons do not know their exact age

The information about age is not precise

Older persons tend to add years to their actual age

Information about handicapped persons is incomplete as many hide them from census enumerators

Information about work status is distorted




Tools of DemographyTools of Demography

Counts Ratios Proportions Rates

CountsCounts

The absolute numbers of a population or any demographic event occurring in a specified time period

Examples − The raw count of

still births − The raw count of

children with diabetes mellitus type 1

− The raw count of people who were born in a barangay

Ratio Ratio A single number that

represents the relative size of the two numbers

K = factor can be 100,1000,10,000 and so on

a & b should be defined for a specific geographic area and period of time

a may not be a part of b

ab

The type of event should be specified

Example;− Sex ratio can be

computed for persons who died due to cancer in 2007, Phils.

k

Ratio Ratio Male deaths due to CA _Female deaths due to CA

ab

Example;− Sex ratio can be

computed for persons who died due to cancer in 2007, Phils.

k

ProportionProportion A special type of

ratio wherein the numerator is a part of the denominator

When k = 100 the proportion becomes a percentage

a

a + b k

ProportionProportion Deaths due to dengue in a given period Total deaths in a given period

a

a + b k

Rate Rate Frequency of

occurrence of events over a given interval of time

Useful for dynamic events (measures amounts of change)

E.g.Incidence

Incidence =No. of events that occurwithin a given time interval

No. of people exposed to the risk of the event during the same time interval

Rate Rate Dengue cases in a

given period__

average population in a given period

x factor

Incidence = No. of events that occur

within a given time interval

No. of people exposed to the risk of the event during the same time interval


Measurable characteristics of people

Sex Age Marital Status Education Occupation

Composition

Describing Population Describing Population CompositionComposition

Age and sex are two most important variables

Have great influence on mortality and morbidity rates

Describing Population CompositionDescribing Population Composition Sex Composition Sex Composition

A. Sex ratio − Compares the number of male individuals to the

number of females in the population

B. Sex structure− Determined by computing for the sex ratio of

each group

Sex RatioSex Ratio Sex ratio = No. of males x 100

No. of females

In the Phils 1990− Sex ratio = 30,443,187 x100

30,155,929

= 101

In the year 1990, in the Phils., there were 101 males for every 100 females in the population

Sex RatioSex Ratio At birth, the ratio is high more males than

females in the younger age group Sex ratio tends to decrease with age

(because more males die during the later ages)

Sex ratio is higher in rural areas than in the urban areas

Frontier communities and colonies have higher sex ratios compared to other communities

Sex StructureSex Structure

Age group(years)

Male Female Sex ratio per 100 females

< 1 16,702 15,661 106.6

5 - 9 59,948 56,718 105.7

10-14 66,093 64,432 102.6

15 -19 59,491 59,238 100.4

20 - 24 56,772 58,629 96.8

Distribution of the Population by Age and Gender, Cavite, 1990

Describing Population CompositionDescribing Population Composition Age CompositionAge Composition

A. Median age− The middle most value (age) in a data set− E.g. 16 years old− Meaning 50% of the population is aged 16 years

old and above and 50% is aged below 16 years

B. Age-dependency ratio

Median AgeMedian Age

024

68

101214

1618

20

1970 1975 1980 1990

Median age

What can be said about the median age in

the Phils ?

Age Dependency RatioAge Dependency Ratio

An index of age-induced economic drain on manpower resources

− Simply relates the size of the dependent segment of the population (very young children + elderly) to the economically productive age-group of the population

Age dependency ratioAge dependency ratio No. of persons 0-14 yrs old +

Age dependency = No of persons aged 65 and > x 100

Ratio No. of persons 15-64 years old

The value represents the number of dependents that need to be supported by every 100 persons in the economically active a group.

Age dependency ratioAge dependency ratio

Faulty assumptions of the formula include

− All children below 15 years and those age 65 and above are considered dependent or economically unproductive

− All persons aged 15- 64 are productive

Age Dependency ratioAge Dependency ratio

Age Group Number Percent

0-14 24,004,586 39.5

15-64 34,629,959 57.1

65 and > 2,063,445 3.4

Table-2 Distribution of the Population by Age Group, Phils., 1990

Compute for the age dependency ratio

Age dependency ratioAge dependency ratio No. of persons 0-14 yrs old +

Age dependency = No of persons aged 65 and > x 100 Ratio No. of persons 15-64 years old

= 24,004,586 + 2,063,445 x 100 34,629,959

= 0.7528 x 100 = 75.3 In 1990, every 100 persons in the economically productive

age group had to support 75 dependents.

Factors Affecting Age Factors Affecting Age Composition of the PopulationComposition of the Population

1. Fertility level− High fertility younger population

2. Peace and order situation

3. Urban-rural differences in fertility level− (urban—more older, rural more younger)


How are people distributed?

Village Town Province...

Distribution

Combined Analysis of Combined Analysis of Age and Sex CompositionAge and Sex Composition

Population pyramid

− A graphical representation of the age and sex composition of the population

− One can describe and explain the demographic trends of the population in the past

Population PyramidsPopulation Pyramids

Types of Population Pyramid

1 2 3 4 5

Type 1 PyramidType 1 Pyramid

Broad base with gently sloping sides

High rates of death and birth

Low median age High dependency

ratio

Percent 0 2 4 6 88 6 4 2 0

0-4

5-9

10-14

15-1920-2425-2930-3435-3940-4445-4950-5455-5960-6465-6970-7475-7980+

Type 2 PyramidType 2 Pyramid Broader base Slanting from 0-4 years

old to the top Beginning to grow

rapidly because of reduction in infant mortality but are NOT yet reducing fertility

Rapid increase in population

Median age is increasing

Percent 0 2 4 6 88 6 4 2 0

0-4

5-9

10-14

15-1920-2425-2930-3435-3940-4445-4950-5455-5960-6465-6970-7475-7980+


Old fashioned “beehive”

Low birth rate Median age is

highest Dependency ratio is

lowest Dependents mostly

elderly Percent 0 2 4 6 88 6 4 2 0

0-4

5-9

10-14

15-1920-2425-2930-3435-3940-4445-4950-5455-5960-6465-6970-7475-7980+


Transitional type Represents a

population after 100 years with declining birth and death rates, has reversed the trend in fertility while maintaining the death rate at low models

Percent 0 2 4 6 88 6 4 2 0

0-4

5-9

10-14

15-1920-2425-2930-3435-3940-4445-4950-5455-5960-6465-6970-7475-7980+


Rapid decline in fertility

Low death rate Reduced its birth

rate very rapidly

Percent 0 2 4 6 88 6 4 2 0

0-4

5-9

10-14

15-1920-2425-2930-3435-3940-4445-4950-5455-5960-6465-6970-7475-7980+

Life Expectancy at BirthLife Expectancy at Birth

Average number of years an infant is expected to live under the mortality conditions for a given year.

Separate for each sex




Population DistributionPopulation Distribution

3 indicators:

1. Urban-rural distribution2. Population density

- no. of people residing in a specific area divided by location size in square km

3. Crowding index- no. of persons divided by no. of rooms in the house- High index high chance of disease transmission

Population Distribution

Urban-rural distribution, Population density

Table 1. Percent Distribution of the Population by Urban-Rural Residence by Region, Philippines, 1990

Region Urban Rural Population Density (per sq. km.)

I Ilocos 37.8 62.2 276.3 II Cagayan Valley 23.5 76.5 87.1 III Central Luzon 60.3 39.7 339.5 IV Southern Taga log 51.1 48.9 175.8 V Bicol 31.2 68.8 221.5 VI Western Visayas 35.8 64.2 266.3 VII Central Visayas 40.4 59.6 306.5 VIII Eastern Visayas 31.2 68.8 142.3 IX Western Mindanao 30.7 69.3 169.1 X Northern Mindanao 43.4 56.6 123.6 XI Southern Mindanao 47.4 52.6 140.4 XII Central Mindanao 25.2 74.8 136.0 NCR 100.0 0 12,433.0 CAR 31.3 68.7 62.4

Measuring Changes in Population Size

Population sizePopulation size

- Changes in population size

- Population estimation

- Tools commonly used to describe changes in population size generally express these changes in terms of increases in population count

Measuring Changes in the Measuring Changes in the


Measures:

1. Natural increase

2. Rate of natural increase

3. Absolute increase

4. Relative increase



Measures:

1. Natural increase

2. Rate of natural increase

*make use of data on just births and deaths

Difference between number of births and number of deaths which occurred within a specified period (usually one year)

Natural increaseNatural increase

Natural Increase = No. of births – No. of deaths

Natural IncreaseNatural Increase

Given: Country XNo. of births in 2011 = 1,684,395

No. of deaths in 2011 = 319,579

Calculate for the Natural Increase in the population of Country X in 2011.

Natural IncreaseNatural IncreaseGiven: Country X

No. of births in 2010 = 1,684,395 No. of deaths in 2010 = 319,579

Calculate for the Natural Increase in the population of Country X in 2010.

=1,684,395 - 319,579 =1,364,816

Interpretation:*A total of 1,364,816 persons were added to the population of Country X in 2010.

Natural IncreaseNatural Increase

Case 1. In 2009, the Philippines had a total of 966,762 live births and 23,038 deaths.

a. Calculate for the natural increase in the population of the Philippines in 2009.

b.Interpret your result.

− When the difference between the number of births and deaths are expressed relative to the population size

Rate of natural increaseRate of natural increase

Rate of Natural Increase = Crude birth rate – Crude death rate

Crude Birth Rate = total no. of livebirths in a yearmidyear population

Crude Death Rate = total no. of livebirths in a yearmidyear population

Rate of natural increaseRate of natural increase

Rate of Natural Increase = Crude birth rate – Crude death rate

X 1000

X 1000

Rate of natural IncreaseRate of natural Increase

Given: Country XCrude birth rate in 2010 = 25.8 per 1000 population

Crude deaths rate in 2010 = 4.9 per 1000 population

Calculate for the Rate of Natural Increase in the population of Country X in 2010.

Rate of natural IncreaseRate of natural IncreaseGiven: Country X

Crude birth rate in 2010 = 25.8 per 1000 population Crude deaths rate in 2010 = 4.9 per 1000 population

Calculate for the Rate of Natural Increase in the population of Country X in 2010.

= 25.8/1000 - 4.9/1000= 20.9/1000 population

Interpretation:There are about 21 persons per 1000 population through natural means were added to the population of Country X

in 2010.

Rate of natural IncreaseRate of natural Increase

Case 1. In 2009, the Philippines had a CBR of 26.4 per 1000 population and a CDR of 6.4 per 1000 population.

a. Calculate for the rate of natural increase in the population of the Philippines in 2009.

b.Interpret your result.



Measures:

3. Absolute increase

4. Relative increase

*make use of population counts obtained during

two censuses

Absolute Increase Per Absolute Increase Per YearYear

– It measures the average number of people added to the population per year

– Numerator = difference between 2 population counts (Pt and Po)

– Denominator = time interval in years between 2 censuses dates (t)

Absolute Increase Per YearAbsolute Increase Per Year

Absolute increase per year = Pt - Po t

Where:Po = population size at an initial time, 0Pt = population size at a latter time, tt = number of years between time 0 and time t


Given: Province X

Population size, 1990 = 771,320

Population size, 2000 = 1,150,458

Calculate for the absolute increase per year of Province X population.


Given: Province X



Calculate for the absolute increase per year of Province X population.

= 1,150,458 - 771,320

10

= 37, 914

Interpretation:

Between 1990 and 2000, there were 37,914 individuals added to the population of Province X each year.

Relative IncreaseRelative Increase

– It is defined as the actual difference between the two census counts expressed in % relative to the population size during the earlier census

Relative Increase Relative Increase

Relative increase = Pt - Po Po

Where:Po = population size at an initial time, 0Pt = population size at a latter time, t100 = factor

X 100

Relative IncreaseRelative Increase

Given: Province X



Calculate for the relative increase per year of Province X population.

Relative IncreaseRelative IncreaseCalculate for the relative increase per year of Province X population.

= 1,150,458 - 771,320

771,320

= 379,138

771,320

= 49.2%

Interpretation: The increase in the population size of Province X between 1990 and 2000 is 49% of its original population that is, the 1990 population.

X 100

X 100

Population ProjectionPopulation Projection

Arithmetic Increase Method

Geometric Increase Method

Population Projection

Is the estimation of the population of any future year.

The chief purpose of projection is to plan for the future requirements of food, schools, transportation, housing, medical care, and the like.


3 ways:

1. Details (total population or aggregate)

2. Time of reference -

3. Type of method


Time of reference - a. Intercensal estimates - population estimates made on any

date intermediate to 2 censuses and take the results of these censuses into account.

b. Postcensal estimates - estimates of population size on any date in the past or during a current date following a census.

c. Projections - population estimates made on any date following the last census for which no current repots are available.


Type of method -a. component - or inflow-outflow or balancing equation method

b. mathematicalb.1 arithmeticb.2 geometricb.3 exponential

Population Projection Arithmetic Progression Method

− Assumes that an equal amount of absolute change occurs in the population every year or that the population growth is the same as 10 years ago

− Steps:1. Determine the population of two censuses2 .Compute for the decennial increase3. Divide this difference (step 2) by 10 (census

years)4. Multiply the result of step 3 with the number of

years projected from the last mentioned census

Example: The population of a village X as per 1991 census was 5,000 and as per 2001 census 6,000. What would be its population on March 1, 2010?

Decennial increase (6,000-5,000) = 1,000The annual increase is 1,000 = 100

10 The number of years from 2001 to 2010 = 9In the next 9 years = 9 x 100 =900The population on March 2010 = 6,000 (base population)

+ 900 = 6,900

Population Projection Arithmetic Progression Method

The population increases on the lines of a cash deposit growing with compound interest.

Assumes that population increase at a constant rate per year.

The principal mathematical operation therefore is the determination of the annual rate of population change.

Population Projection Geometric Progression Method

Example: The population of a Village X as per 1991 census was 5,000 and as per 2001 census 6,000. What would be its population on March 1, 2010?

Task: Project the population of Village X in the year 2010 if the census in as per 1991 census was 5,000 and as per 2001 census was 6,000.

Solution:

To compute for the population in 2010, one can use either 1991 or 2001 census as the base population.


Let Pt = the population in 2010 r = annual rate of increase in %


Pt = Po (1 + r)t

Let Pt = the population in 2010 r = annual rate of increase in %

Step 1. Compute for the rate of change= Census of 2001 – Census of 1991 ÷ time interval (yrs) x 100

Census of 1991

= 6,000 – 5,000 ÷ 10 years x 100 5,000

= 2%

Interpretation: The population therefore is increasing by 2% in a compound interest fashion.


2001 population is = 6,0002010 population is = Pt

Difference in years = 2001 – 2010 = 9 yearsPt = 6,000 X (1 + .02)9 Consulting the compound interest table,the value of 1 growing at 2%

annually in 9 years is 1.19509

Hence the population at 2010 = 6,000 x 1.19509= 7,170.36 or 7171

If the compound table is not available, simply add 1 plus .02 = 1.02And multiply 6,000 by 1.02 by nine times. (in contrast to the computed 6,900 of the arithmetic method)


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Principles of Demography.pdf