1 population projections session 8 - projections for sub- national and sectoral populations ben...

11

POPULATION PROJECTIONSPOPULATION PROJECTIONS

Session 8 - Session 8 - Projections for sub-Projections for sub-national and sectoral populationsnational and sectoral populations

Ben JarabiBen Jarabi

Population Studies & Research InstitutePopulation Studies & Research Institute

University of NairobiUniversity of Nairobi

22

The need for sub-national projectionsThe need for sub-national projections

Sub-national structures need projected Sub-national structures need projected population to quantify likely need and to population to quantify likely need and to help plan for serviceshelp plan for services

National governments need projected pop. National governments need projected pop. to allocate resources throughout the to allocate resources throughout the countrycountry

Ministries need projected population to Ministries need projected population to implement and monitor programmesimplement and monitor programmes

The private sector may be interested in the The private sector may be interested in the growth of specific age groups and in the growth of specific age groups and in the growth of households, both of which drive growth of households, both of which drive consumptionconsumption

33

Sub-national projectionsSub-national projections

Subnational projections - use either a Subnational projections - use either a

cohort-component procedure or one of a cohort-component procedure or one of a

number of simpler, less data-demanding number of simpler, less data-demanding

methodologies methodologies

Cohort-component projection, which Cohort-component projection, which

requires all of the inputs of national requires all of the inputs of national

projections plus internal migration by age projections plus internal migration by age

and sexand sex

Mathematical or ratio projection, with or Mathematical or ratio projection, with or

without age-sex detailwithout age-sex detail

44


Because of the Because of the data and computational data and computational

requirementsrequirements involved, we typically see, involved, we typically see,

and is generally recommended that the and is generally recommended that the

cohort-component projection be applied at cohort-component projection be applied at

no lower than first subnational no lower than first subnational

administrative leveladministrative level

Ratio projection suffices at lower than first Ratio projection suffices at lower than first

subnational administrative levelssubnational administrative levels

55


Generating sub-national projections that are Generating sub-national projections that are

both both internally consistent and consistent with internally consistent and consistent with

a national projectiona national projection is usually more is usually more

challenging than preparing a national challenging than preparing a national

projectionprojection

Each region presents the same data problems Each region presents the same data problems

as the national projection but, in addition, as the national projection but, in addition,

preserving consistency across regions and preserving consistency across regions and

dealing with data problems that are often dealing with data problems that are often

more severe than those at the national level more severe than those at the national level

adds to the challengeadds to the challenge

66


A national projection can be generated as A national projection can be generated as the sum of a series of sub-national the sum of a series of sub-national projections, or a national projection may be projections, or a national projection may be prepared first, followed by sub-national prepared first, followed by sub-national projections with the region with the largest projections with the region with the largest population serving as residualpopulation serving as residual

For a given country, a hybrid of For a given country, a hybrid of procedures may be used. For example, procedures may be used. For example, projections for major regions can be projections for major regions can be combined into a national projection and combined into a national projection and can serve as separate control totals for can serve as separate control totals for provincial or district projectionsprovincial or district projections

77


Data RequirementsData Requirements Census age-sex structure andCensus age-sex structure and

For cohort-component projection:For cohort-component projection: Fertility and trendFertility and trend Mortality and trendMortality and trend Internal migration and trendInternal migration and trend International migrationInternational migration, ,

oror

For mathematical or ratio projection:For mathematical or ratio projection: Trend in population totalsTrend in population totals

88


Begin with base year age-sex structureBegin with base year age-sex structure

Adjust for coverage if possibleAdjust for coverage if possible

Adjust for consistency of under-10 Adjust for consistency of under-10 population with fertility and mortalitypopulation with fertility and mortality

Smooth at ages 10+ if need beSmooth at ages 10+ if need be

Ensure that regions add to national totals Ensure that regions add to national totals by age and sexby age and sex

Resulting age-sex structure provides initial Resulting age-sex structure provides initial population for forcing base-year population for forcing base-year consistency between fertility and mortalityconsistency between fertility and mortality

1010


Cohort-Component Method - SummaryCohort-Component Method - Summary

This method is widely used, relatively easy This method is widely used, relatively easy

to explain, and practicalto explain, and practical

It permits the use of already available data It permits the use of already available data

and existing theoretical knowledge on the and existing theoretical knowledge on the

dynamics of population growth, and it takes dynamics of population growth, and it takes

into account causal factors, at least at the into account causal factors, at least at the

level of basic components and compositional level of basic components and compositional

factorsfactors

1111


Cohort-Component Method - SummaryCohort-Component Method - Summary It has the capability to produce consistent & It has the capability to produce consistent &

comparable national & subnational comparable national & subnational projections that are easy to update on a projections that are easy to update on a regular basisregular basis

Much of the work required to use this Much of the work required to use this method lies in the in-depth analysis and method lies in the in-depth analysis and development of assumptions for each of the development of assumptions for each of the components of changecomponents of change

However, it also has its shortcomings and However, it also has its shortcomings and limitations, e.g. it does not explicitly limitations, e.g. it does not explicitly incorporate socioeconomic determinants of incorporate socioeconomic determinants of population changepopulation change

1212


Ratio Method - SummaryRatio Method - Summary

This method suffers from several This method suffers from several

shortcomingsshortcomings

They do not account for differences in They do not account for differences in

demographic composition or for differences demographic composition or for differences

in the components of growthin the components of growth

They provide little or no information on the They provide little or no information on the

projected demographic characteristics of the projected demographic characteristics of the

populationpopulation

1313


Ratio Method - SummaryRatio Method - Summary This method suffers from several shortcomingsThis method suffers from several shortcomings

Because they have no theoretical content, they Because they have no theoretical content, they cannot be related to theories of population cannot be related to theories of population growth, except perhaps the logistic model, which growth, except perhaps the logistic model, which is consistent with a Malthusian view of is consistent with a Malthusian view of population dynamicspopulation dynamics

Consequently, they have limited usefulness for Consequently, they have limited usefulness for analyzing the determinants of population growth analyzing the determinants of population growth or for simulating the effects of changes in or for simulating the effects of changes in particular variables or assumptionsparticular variables or assumptions

In addition, they can lead to unrealistic or even In addition, they can lead to unrealistic or even absurd results, even over relatively short absurd results, even over relatively short horizonshorizons

1414

Sectoral projectionsSectoral projections

Projections of households, school enrollment, Projections of households, school enrollment,

poverty, employment, health, and other poverty, employment, health, and other

population-related characteristics are needed population-related characteristics are needed

for many types of planning, budgeting, and for many types of planning, budgeting, and

analysis - analysis - for simplicity, these are referred to for simplicity, these are referred to

as as socioeconomicsocioeconomic projectionsprojections

Because of the demand for socioeconomic Because of the demand for socioeconomic

projections and their close link to projections projections and their close link to projections

of basic demographic characteristics, the of basic demographic characteristics, the

former are often made on the basis of the former are often made on the basis of the

latterlatter

1515


Projections of socioeconomic Projections of socioeconomic

characteristics, however, has two characteristics, however, has two

important features that distinguish them important features that distinguish them

from strictly demographic projectionsfrom strictly demographic projections

One, some socioeconomic characteristics are One, some socioeconomic characteristics are

directly affected by policy decisions - e.g. directly affected by policy decisions - e.g.

enrollment is usually dictated by entrance enrollment is usually dictated by entrance

requirementsrequirements

In such instances, knowledge of public policy In such instances, knowledge of public policy

is essential to the production of projections is essential to the production of projections

of socioeconomic characteristicsof socioeconomic characteristics

1616


Two, projections of socioeconomic Two, projections of socioeconomic

characteristics involve achieved characteristics involve achieved

characteristics - those that can change over characteristics - those that can change over

one’s lifetime, e.g. marital status, income, one’s lifetime, e.g. marital status, income,

educational attainment, occupationeducational attainment, occupation

As a result, projections of As a result, projections of

socioeconomic characteristics involve a socioeconomic characteristics involve a

variety of assumptions in addition to variety of assumptions in addition to

those for projections of strictly those for projections of strictly

demographic characteristicsdemographic characteristics

1717


Two fundamental approaches are Two fundamental approaches are

frequently used to prepare frequently used to prepare

socioeconomic projectionssocioeconomic projections

Participation ratio methodParticipation ratio method

Cohort-progression methodCohort-progression method

1818



In this approach, socioeconomic In this approach, socioeconomic

characteristics are related to demographic characteristics are related to demographic

characteristics through the use of ratioscharacteristics through the use of ratios

Current and historical data are used to Current and historical data are used to

construct participation ratios – i.e., construct participation ratios – i.e.,

proportions of the population (stratified by proportions of the population (stratified by

age, sex, and perhaps other demographic age, sex, and perhaps other demographic

characteristics) that have the socioeconomic characteristics) that have the socioeconomic

characteristic of interestcharacteristic of interest

1919



Once such ratios are established, they can Once such ratios are established, they can

be projected in a number of ways, be projected in a number of ways, e.g. e.g.

holding them constant at recent levels, holding them constant at recent levels,

extrapolating recent trends, or tying them to extrapolating recent trends, or tying them to

ratios found in other areasratios found in other areas

The projected ratios are then applied to The projected ratios are then applied to

population projections for the geographic population projections for the geographic

area(s) under consideration to obtain a set area(s) under consideration to obtain a set

of socioeconomic projections of socioeconomic projections

2020


Cohort-progression methodCohort-progression method In this approach, projections are developed by In this approach, projections are developed by

“surviving” people with particular socioeconomic “surviving” people with particular socioeconomic characteristicscharacteristics

The numbers with the socioeconomic The numbers with the socioeconomic characteristic or the corresponding participation characteristic or the corresponding participation ratios are projected on a cohort basis using ratios are projected on a cohort basis using information on changes in the numbers or information on changes in the numbers or participation ratios between two previous datesparticipation ratios between two previous dates

The conventional form of this method uses ratios The conventional form of this method uses ratios of the number of persons aged of the number of persons aged aa with a with a particular socioeconomic characteristic in year particular socioeconomic characteristic in year tt to the number of persons aged to the number of persons aged a a - - yy with that with that characteristic in year characteristic in year t t - - yy

2121


Cohort-progression methodCohort-progression method It is important to remember that cohort It is important to remember that cohort

progression ratios represent net cohort progression ratios represent net cohort change rather than gross changechange rather than gross change

This distinction is important because This distinction is important because fundamental patterns may be masked fundamental patterns may be masked without knowing the numbers “entering and without knowing the numbers “entering and exiting” a populationexiting” a population

The cohort-progression method in the form The cohort-progression method in the form of participation ratios is used less often than of participation ratios is used less often than the version of the method that employs the version of the method that employs absolute numbers absolute numbers

1 population projections session 8 - projections for sub- national and sectoral populations ben...

Documents

national totals

national level

subnational projectionsbegin

inputs of national projections

national projectioneach

population totals

projected population

district projections