Session 7: Population projections for national populations

• 7.1. Spectrum• 7.2. Evaluation of projection results• 7.3. Accounting for uncertainty

– choosing alternative projection scenarios• 7.4. Lab time

7.1.2. 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

7.1.2. Using Spectrum

SPECTRUM is at version 4.51.

As it under continuing development, one should check for updates online:

http://www.futuresinstitute.org/spectrum.aspx

7.1.2. Using Spectrum

Spectrum

7.1.2. 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

7.1.2. Using Spectrum

• Steps:• 1. Projection parameter settings • 2. Data input• 3. Executing the projection• 4. Obtaining, saving the results

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

Trouble shooting Spectrum

• Spectrum stores results in files with the extension *.dp

• By renaming the file to *.csv, it can directly be opened by Excel

7.2. 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 – 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 characteristics3.External Consistency– The projection makes sense compared to contextual and/or

comparison areas

7.3. Accounting for uncertainty -- Choosing alternative projections

scenarios

• Reasons for uncertainty• How to account for uncertainty?• Construct scenarios• Project past variability• Expert opinions

Reasons for uncertainty

• Open future – several options for future trends• Input data• Assumptions

How to account for uncertainty?

• Construct scenarios• Probabilistic projections:

– Project past variability– Expert opinions

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. Name it accordingly: BeninConst. • Or simply use the medium variant available in Spectrum

as a starting point. Name it BeninMedium.• 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 BeninConstant.

• Spectrum has now two projections loaded: BeninMedium and BeninConstant. BeninConstant is right now only a copy of BeninMedium, so we have to make changes to the fertility settings in BeninConstant.

• Make sure that BeninConstant 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 BeninMedium, and one named BeninConstant.

Hands-on exercise: Scenarios• Now you may add even more scenarios.• As the first scenario (BeninMedium) is the reference

scenario, set BeninMedium to be the active projection.

• Now re-load BeninMedium, and chose Load and rename.

• Rename it to BeninInstant.

Hands-on exercise: Scenarios• What do the scenarios reveal about the

demographic future of the country chosen?• Discuss the results.

7.4.Lab time

Thank you