Transcript International Workshop on Population Projections using Census Data 14 – 16 January 2013 Beijing, China.

International Workshop
on
Population Projections
using Census Data
14 – 16 January 2013
Beijing, China
Session VI:
Population projections for national
populations
• Tools for the preparation of national
projections
• Preparing the data and formulating
assumptions
• Dealing with uncertainty: variants and
illustrative scenarios
http://unstats.un.org/unsd/demographic/meetings/wshops/China2013/list_of_docs.htm
Tools for the preparation of
national projections
Overview
Tools for the preparation of national
projections
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Spectrum (Futures Institute)
RUPEX (US Census Bureau)
MORTPAK (UN Population Division)
LIPRO (NIDI)
PEDA (IIASA)
Tools for the preparation of national
projections: Newcomer
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ProFamy (China)
PADIS (China)
PPPD/P3J (Uni Rostock)
MICMAC (Europe)
Preparing the data and formulating
assumptions
• Before a projection can be produced, data
need to be collected, analyzed and, if
necessary, adjusted (see previous Sessions)
• It is important to also collect time series of
demographic data in order to have a sound
basis for the formulation of projection
assumptions.
Preparing the data and formulating
assumptions
• As minimum, the following data need to at
hand:
– Population by age and sex for the base year (start
year, jump-off year)
– Age specific fertility data for the period
immediately before the base year
– Age specific mortality data (or life tables) for the
period immediately before the base year.
– Total net migration for the period immediately
before the base year, by age and sex if possible.
Preparing the data and formulating
assumptions
• Based on the data available, assumptions for
fertility, mortality and net migration need to
be formulated.
• In order to account for uncertainty, variant
assumptions may be formulated.
• The tools presented in Sessions IV and V can
be sued to calculate future trends of fertility,
mortality and migration.
Preparing the data and formulating
assumptions
• The data prepared need to be entered into a
projection software.
• The steps to enter and carry out projections
are shown in the follwoing.
Using Spectrum
SPECTRUM is a suite of easy to use policy models which provide policymakers with an
analytical tool to support the decision making process.
SPECTRUM consists of several software models including:
•DemProj: Demography
•FamPlan: Family Planning
•LiST: Lives Saved Tool (Child Survival)
•AIM: AIDS Impact Model
•Goals: Cost and impact of HIV Intervention
•Resource Needs Module: Costs of implementing an HIV/AIDS program
•RAPID: Resources for the Awareness of Population Impacts on
Development
•Safe Motherhood Model
•Allocate
Using Spectrum
• SPECTRUM is at version 4.51 4.53 Beta 35
(07.01.2013).
• As it is under continuing development, one
should check for updates online:
• http://www.futuresinstitute.org/spectrum.aspx
Using Spectrum
Spectrum
Using Spectrum
• Advantages:
– Reliable and well tested
– Appealing user-interface
– User base is large, but concentrated among health
and policy professionals (UNAIDS)
– Support, on-site Training available
• Disadvantages
– Complex package due to integration into a variety of
other tools (AIDS, POLICY etc.)
– Obtaining results can be cumbersome
Using Spectrum
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Steps:
1. Projection parameter settings
2. Data input
3. Executing the projection
4. Obtaining, saving the results
Preparing the data and
formulating assumptions
Overview
Hands-on exercise:
Preparing a cohort-component
projection with Spectrum
Hands-on exercise
• Executing the sample projection and
examining the results
• Preparing a new projection
• Adding data
• Obtaining results from Excel
Using Spectrum 1
Sample.pjn
Using Spectrum 2
Using Spectrum 3
Projection menu
group
Using Spectrum 4
Set last year
Uncheck AIDS
Using Spectrum 5
Using Spectrum 6
Using Spectrum 7
Using Spectrum 8
Using Spectrum 9
Using Spectrum 10
Using Spectrum 11
Using Spectrum 12
Using Spectrum13
Using Spectrum 14
Using Spectrum 15
• Spectrum stores results in files with the
extension *.dp
• By renaming the file to *.csv, it can directly be
opened by Excel
Dealing with uncertainty:
variants and illustrative scenarios
Overview
Dealing with uncertainty: variants and
illustrative scenarios
• Population projections are constraint by the
imperfect knowledge of current and future
demographic settings and trends. Although
the demographic momentum inherent in
demographic dynamics has allowed
demographers to produce demographic
projection with a comparatively high quality, it
is impossible to make a perfect projection.
Dealing with uncertainty: variants and
illustrative scenarios
• A traditional and well accepted way to incorporate
uncertainty into population projections is the
preparation of projections variants that show a certain
range of results that is deemed plausible.
• Another, more recent approach is using the ubiquitous
computer power of modern computing equipment to
create probabilistic projections consisting of many
possible demographic pathways. It should be noted
that the probabilistic approach is still a field under
development.
Dealing with uncertainty: variants and
illustrative scenarios
• Scenarios are yet another way to illustrate
future demographic trends. Scenarios are
created by describing a future in a qualitative
way, and then constructing corresponding
demographic trends. Scenarios are then the
answer to a “What if?” question
Dealing with uncertainty: variants and
illustrative scenarios
• Common scenarios
– Constant fertility
– Constant Mortality
– No migration
– Instant replacement
Hands-on exercise:
• Preparing and comparing different projection
variants
Hands-on exercise: Scenarios
• Spectrum: Comparison Projections
• Start by creating a Projection, using data in Spectrum.
• You may modify the data as you wish: Set fertility to
constant, for example
• Or simply use the medium variant available in Spectrum
as a starting point. Name it UgandaMedium.
• Select an appropriate base year (2010?).
• Select an appropriate last year (2050?)
• Inspect the settings. Save the projection
• Next add more scenarios.
Hands-on exercise: Scenarios
• Add another scenarios.
• You could just create another projection input file,
apply your scenario setting and save it with an
appropriate name.
• There is a shortcut: Open the file you just saved
again. Spectrum gives you a choice. Click on Load
and rename.
Hands-on exercise: Scenarios
• We want the second scenario to keep fertility levels
constant at base level. Name the second scenario
UgandaConstant.
• Spectrum has now two projections loaded:
UgandaMedium and UgnadaConstant.
UgandaConstant is right now only a copy of
UgandaMedium, so we have to make changes to
the fertility settings in UgandaConstant.
• Make sure that UgandaConstant is set to be the
active projection.
Hands-on exercise: Scenarios
• In order to keep the fertility constant, you can
either copy the base fertility to the projection years,
or use Spectrum’s copy and duplicate functions:
• Highlight the fertility and click Duplicate.
• Check if the fertility has been changed: Go to results
and look at the fertility chart.
• Note that there are now two fertility trends, one
named UgandaMedium, and one named
UgandaConstant.
Hands-on exercise: Scenarios
• Now you may add even more scenarios.
• As the first scenario (UgandaMedium) is the
reference scenario, set UgandaMedium to be the
active projection.
• Now re-load UgandaMedium, and chose Load and
rename.
• Rename it to UgandaInstant.
Hands-on exercise: Scenarios
• What do the scenarios reveal about the
demographic future of the country chosen?
• Discuss the results.
Evaluation of projection results
Projections are about the future, and therefore are invariably
incorrect. It would not be useful to evaluate them in terms of their
correctness (accuracy). Instead, one should assess them differently:
1. Sound Methodology
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2.
Internal Consistency
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3.
The projection makes sense relative to the characteristics and
assumptions of the methods
The projection makes sense compared to historical demographic
patterns
The projection makes sense compared to local socioeconomic/
cultural characteristics
External Consistency
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The projection makes sense compared to contextual and/or
comparison areas
Lab time
• Create a new projection using your own data.
• Hint: You may use the projection available in
Spectrum and change only those indicators
you have data for.
Thank you