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Session I. Introduction7 March 2016
Cheryl Sawyer, Lina BassarskyPopulation Estimates and Projections Section
www.unpopulation.org
Regional Workshop on the Production of Population ProjectionsAddis Ababa, 7-11 March 2016
I. Introduction to population projections
Why population projection?o Produce internally consistent demographic estimates
using population, fertility, mortality and migration trendso Understanding the determinants of population changeo Planning for people’s needs
– Education– Health system– Social Security– Employment– Infrastructure – Housing
o Establish population policies, such as promoting family planning or setting immigration policies
Future is unknown, but we know some basic demographic trends
o Demographic processes are long-term– Lasting impact of past and current changes– Momentum
o No equilibrium yet– Demographic changes continue in all areas of the
world
o Demographic transition as guiding principle– Countries move from high fertility and mortality to low
fertility and mortality – still in progress in many developing countries
The demographic transition animated
The demographic transition animated
Transformation of age structures:=> From pyramid to (almost) rectangle.
=> From young populations to older populations
World population aging
Source: UN World Population Prospects: 2015 Revisionestimates and projections
Transformation of survival:=> From early deaths to late deaths.
Changing survivalDeaths by age and sex, World
Source: UN World Population Prospects: 2015 Revision estimates and projections
What can population projections reveal?
Planning for immunization, education, etc.
Population under age 15 would double within 30 years if today’s fertility remain unchanged
UN World Population Prospects: 2015 Revision estimates and projections
Constant fertility
No change
High
Medium
Low
Instant replacement
Planning for housing and work
Source: UN World Population Prospects: 2012 revision estimates and projections
Doubling within 25 years under most scenariosDoubling within 25 years under most scenarios
Source: UN World Population Prospects: 2015 Revision estimates and projections
Constant fertilityNo changeHigh
Medium
Low
Instant replacement
Who needs, who uses population projections?
Main userso Central governments (ministries of education,
health, planning, etc.)o Regional and local governmentso Private sector (demand, supply)o Academics
Producers of population projections
o Governments: NSO, other national institutionso Regional organizations: EUROSTAT, CELADE
(UN Regional Commission)o International organizations: United Nations
Population Division (World Population Prospects, World Urbanization Prospects)
o Others: Private sector, international research institutions (IIASA), US Census Bureau (International Programs Center)
Projections vary by user needs
o Geography– Local– National– Global
o Time horizon– Short-term– Medium-term– Long-term
Projections vary by user needs
o Selection of variants/scenarios, e.g.:– Slow vs. fast fertility decline– Slow vs. fast mortality decline– High vs. low net migration
o Outputs, e.g.:– Total population– Population by age and sex– Population by other characteristics
• Education• Health• Labour force• Household size
“Projections” and “Forecasts”What’s the difference?
o Population projection:– A computational procedure to calculate population
size and structure at one time from population size and structure at another, together with a specification of how change takes place during the interim period.
o Population forecast: – A projection based on assumptions that are predictive
and considered to yield the most probable estimates of the future development of a population.
o Scenarios or variants
Overview of the UN MethodologyWorld Population Prospects
(the 2015 Revision was released in July 2015)
o Estimates and projections of population and demographic components for all countries of the world, 1950-2100
o Estimates vs. projections
o Demographic components: Fertility, mortality, international migration
o De facto concept
refresh
Overview of the UN World Population Prospects
o Our users– UN system– General users throughout the world– Researchers
o Geography– 233 countries or areas– Full data published for 201 countries or areas >90,000
population in 2015
UN population estimates by age and sex
o Base year is 1950o Populations by age and sex generated using the cohort-
component method and information on the different components of the population (e.g. fertility, mortality and migration)
o Results checked against population counts that are made available over time
o This process enables us to maintain consistency between the different components and the overall population
o On the basis of the consistency check, adjustments are sometimes required
refresh
Consistency checking: illustration
Census 1960
Census 1970
Population projections by age and sex
o Base year of projections is 2015o “Medium variant” projection uses the cohort-component method and
expected future paths of fertility, mortality and international migration.
o Statistical techniques are used to determine the expected paths of future fertility and mortality; general guidelines are used to project international migration
o Different variants and scenarios are added to the “medium” projection to illustrate the effect of changes in the assumptions
– Two examples: constant fertility scenario; zero-migration scenario o More recently, a probabilistic approach was added to the projection
of total fertility and life expectancy at birth by sex.o In some cases, deviations from the standard projection procedures
are necessary, for instance, to account for the relatively high prevalence of HIV/AIDS in some countries.
80% and 95% prediction intervals
Source: United Nations, World Population Prospects: The 2015 Revision, 2015
Output – Global population
24
Output – Population by age and sex
Example for Zambia
Output – Country profiles
Example for Zambia
Output – Mapshttp://esa.un.org/unpd/wpp/Maps/
Output – Interactive datahttp://esa.un.org/unpd/wpp/DataQuery/
Output – Download centrehttp://esa.un.org/unpd/wpp/dvd/
II. Population projections in the African context
Majority of future global population growth will occur in Africa
0
1
2
3
4
5
6
Africa Asia Europe Latin America and theCaribbean
Northern America Oceania
Popu
latio
n (billions)
1990
2015
2030
2050
2100
Source: World Population Prospects: The 2015 Revision
The demographic transition in Africa
The demographic transition in Africa
Demography and the global development agenda
o Demographic dividend– Fertility declines lead to rise in proportion of population in
working ages, favourable dependency ratios– Opportunity for social and economic development
o 2030 Agenda for Sustainable Development – 17 Sustainable Development Goals, 169 targets– Indicator framework under discussion at UN Statistical
Commission– 2016 Commission on Population and Development theme:
“Strengthening the demographic evidence base for the post-2015 development agenda”
The ability to realize sound population projections will assist governments in planning and monitoring their national development.
Challenges to realizing sound population projections
o Challenges in availability and quality of datao Challenges in estimating baselines for the
demographic components (population, fertility, mortality, migration)
o Challenges in making projection assumptions for the components
Challenges for estimating baselines for population projections (UN example)
Number of countries in Africa according to the most recent data used for estimations in WPP 2015
Data on:
Num. of countries Fertility
Child Mortality
Adult Mortality
Population
No information ‐ 1 33 ‐Before 1990 ‐ ‐ ‐ 31990‐1994 ‐ 1 1 11995‐1999 ‐ ‐ 1 ‐2000‐2004 ‐ ‐ 5 62005‐2009 9 17 8 212010 or later 48 38 9 27Total Africa 57 57 57 58
Source: UN/DESA, Population Division (2015). World Population Prospects: The 2015 Revision, Methodology of the United Nations Population Estimates and Projections, Working Paper No. ESA/P/WP.242
Data availability
Challenges for estimating baselines: Population
o Census data quality– Undercount – Age misreporting
• Both undercount and age misreporting may be differential by age/sex
Challenges for estimating baselines: Fertility
o Vital registration missing or incompleteo Survey data on birth histories
– More frequent in recent decades– Sampling error– Non-sampling error
o Census data on recent births– Tend to be underreported– Different adjustment techniques give different results
Challenges for estimating baselines: Fertility
Total fertility estimates in Ethiopia based on different censuses and surveys
Challenges for projection assumptions: Fertility
o Fertility in many African countries has declined later and more slowly compared to experience of other parts of the world
o Existing models for projection of fertility decline tend to assume faster decline
Total Fertility: 1950‐2015 estimates
Source: World Population Prospects: The 2015 Revision
Challenges for estimating baselines: Life expectancy
o Vital registration missing or incompleteo Census life tables from household deaths
– Infrequent– Require careful assessment of data quality
o Other sources of mortality estimates (demographic surveys; indirect questions) do not cover the full age span– Need to combine estimates or select model life table
Challenges for estimating baselines: Child mortality
o Methods for estimating child mortality are well developed
o Survey data on birth histories– Collected frequently in recent decades– Sampling error– Non-sampling error
o Indirect estimates (Children ever born/children surviving)
o Childmortality.org database provides unified dataset, methodology
Source: www.childmortality.org
Central African Republic
Estimates of the UN Inter‐agency Group for Child Mortality Estimation
www.childmortality.orgDeaths un
der a
ge 5 per 1,000
live births
Challenges for estimating baselines: Adult mortality
o Amount of data available is increasing– Household deaths from censuses– Indirect estimates (e.g. orphanhood)– Direct estimates from sibling survival histories
collected in surveyso Analytical results often inconclusive
Challenges for projection assumptions: Mortality
o Recent rapid improvements in child mortality– Should pace of decline continue?
o Adult mortality declines likely not keeping pace– Model life tables assume child and adult mortality
decline are correlatedo HIV/AIDS
– Large impact of HIV/AIDS mortality in 1990s/2000s– More recently: reductions in HIV prevalence,
widespread availability of anti-retroviral therapy (ART)
Acceleration in reduction of under‐five mortality
Source: UN Inter‐agency Group for Child Mortality Estimation. Levels & trends in child mortality: Report 2015
Challenges for baselines and projections: Migration
o Limited data on migration– Place of birth or previous residence in census– Administrative data– Refugee data
o Not possible to predict sudden movements; trends can fluctuate very quickly
III. Overview of workshop materials & tools
Materials providedo Folder for each session
– Presentations– Exercises– Spreadsheets/tools for that session
o Tools– Spectrum 5.40– Mortpak 4.3– US Census Bureau tools
• RUP/DAPPS• PASEX• Subnational Toolkit
– Manuals and texts (UN and other)– WPP2015 publications
Thank you
Questions?>> until 11 March:
>> After 11 March: [email protected]@un.org
Regional Workshop on the Production of Population ProjectionsAddis Ababa, 7-11 March 2016
