International Workshop on Population Projections using Census Data

International Workshop on

Population Projectionsusing Census Data

14 – 16 January 2013Beijing, 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

Tools for the preparation of national projections

Overview

Tools for the preparation of national projections

• Spectrum (Futures Institute)• RUPEX (US Census Bureau)• MORTPAK (UN Population Division)• LIPRO (NIDI)• PEDA (IIASA)

Tools for the preparation of national projections: Newcomer

• ProFamy (China)• PADIS (China)• PPPD (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. • 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

• 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

Uncheck AIDS

Set last year

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 resultsProjections 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 – The projection makes sense relative to the characteristics and

assumptions of the methods2. Internal Consistency

– The projection makes sense compared to historical demographic patterns

– The projection makes sense compared to local socioeconomic/ cultural characteristics

3. External Consistency– 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