Ludi Simpson University of Manchester 21112014 The survey reveals widespread and growing interest in demographic prospects particularly strong in the Health Service and Local Government Only a minority of users looked very far ahead ID: 429298
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Slide1
Why do we forecast?
Ludi Simpson, University of Manchester, 21/11/2014
“The survey reveals widespread and growing interest in demographic prospects, particularly strong in the Health Service and Local Government. Only a minority of users looked very far ahead.
“While customers are on the whole satisfied with official projections, the need for better local projections was a recurrent theme. Information on internal migration, and variant assumptions about its course were in strong demand, as were better and more up-to-date baseline data on the present.
“Improved methodology for local projections and training in it is called for.”Slide2
Summary
3 case studies“Predict what you cannot control, plan what is under your control”
Which plans need forecasts?
What is it about population that is not under the planner’s control?
Planning scenarios – what is possible?
How to deal with intrinsic uncertainty in the prediction?Slide3
Case Study: National Parks in Britain
Zero total net migration, but young adults replaced by older families
Cairngorms National Park
Peak District National Park
(Source: Marshall and Simpson, 2009)Slide4
Peak District National Park
A reduced and elderly population, fewer of working age, requiring more housing, Slide5
Case Study: South East Wales
Welsh government 2011-based population projections
Greater growth
National centre Cardiff attracts from de-industrialised valleysSlide6
Case Study: South East Wales
OAN is based on satisfying the continuation of recent trendsAlternative scenarios envisage more balanced development
Welsh government 2011-based household projections with variant population assumptions - CardiffSlide7
Case study: Birmingham ethnic composition
Population change 2001-2026
Change can be decomposed into each
component
A young age structure has intrinsic momentum
for increase
Increasing ethnic diversity outside the control of planners
Source: BCC report 2006Slide8
“Predict what you cannot control, plan what is under your control” RJS Baker
Why do we forecast?Which plans need forecasts?What is it about population that is not under the planner’s control?
Planning scenarios – what is possible?
What if the prediction is uncertain? Slide9
Which plans need forecasts?
(source: Joshi and Diamond, 1990)
% of sector using forecasts for each reason (column=100%)
Central
govt
Local Govt
Health
Consult/ Market
Res
PrivateRecruitment/ personnel33223318
60Marketing
11
14
6
47
52
Investment
17
15
10
24
31
Location
11
19
27
41
38
Transport
28
63
2
53
6
Planning
56
97
59
65
2
Housing
28
78
4
41
10
Education
22
73
0
18
10
Welfare/Health
28
71
100
18
4
Elderly
39
75
41
6
4
Children
33
75
41
12
2
Research
39
54
51
53
21
Teaching
6
10
14
6
2
Other uses
44
31
20
29
8Slide10
What is it about population that is not under the (
local) planner’s control, and therefore should be predicted?
Fertility and mortality?
Almost always considered not locally plannable
Therefore a ‘trend’, or ‘business as usual’ projection is used as a prediction, informed by expected long-term national trend
Usually predicted locally by applying trends from national projection
The official projection is usually used
Occasionally local data establish the recent experience
International migration?
Debatable influence of planners at national scaleTaken as not under planners’ control at local scale (?)The official projection is usually used: ‘trend’, or ‘business as usual’Slide11
Can planners control internal migration (within UK)?
National town planning policy assumes that internal migration is affected by the local strategic plan
Extra (or restricted) housing brings extra (or fewer) residents
Extra (or restricted) jobs bring extra (or fewer) residents
For other planners (adult care, schools, youth service, store location, recruitment and personnel, ...), internal migration is not under their influence
Accept the ‘business as usual’ projection
Or the local plan once adopted
For the projectionist, a tale of many
guvnorsScenarios, projections, forecasts, predictionsSlide12
Planning scenarios – what is possible?
Extra (or restricted) housing brings extra (or fewer) residents
How many extra or fewer residents?
Answer not provided by the official projections (“business-as-usual”)
Software provides answers (POPGROUP,
Chelmer
, ...)
How do households translate into need for housing?
Vacant housing, second or holiday homesHow does the labour force translate into filling jobsCommuting, unemployment
Migration flows are adjusted to fill the extra housing or jobs
www.ccsr.ac.uk/popgroupSlide13Slide14
Current National Planning Framework Policy (NPPF)
Objectively assessed housing needBased on the official projection of population and households (trend, business as usual)
updated with the most recent demographic information
Various possible upward adjustments (See PAS June 2014)
Suppressed housing supply in past; special circumstances; expected jobs development
Disputed at examinationsSlide15
Current National Planning Framework Policy (NPPF)... continued
Housing targetsPlanning adjustments to Objectively Assessed Housing Need
To achieve national policies such as Green Belt, environmental protection and local aspirational additional jobs growth
To achieve local policies that may increase housing provision
All downward adjustments must be compensated for in other (usually neighbouring) districts
Duty to co-operate
“At the heart of the National Planning Policy Framework is a presumption in favour of sustainable development, which should be seen as a golden thread running through both plan-making and decision-taking” Slide16
What if the prediction is uncertain?
The prediction is intrinsically uncertainSNPP average error measured against 2006 MYE:
ONS 2008
Subnational population projections accuracy report
For LAs, average error about 0.5% per year of projection
But it does not show the error for different sizes and characteristics of LA
Years ahead projected: 2 2 3 6 8 10Slide17
Recommendation to local projectionists: sensitivity test for plausible uncertainty
Penultimate extreme values from past decadeFertility
Mortality
Migration within UK
Migration with overseas
Other plausible alternatives to the prediction
ONS high and low fertility and mortality variants
Migration from early 2000sSlide18
ONS 2010-based NPP, publication on variants (2012)Slide19
ONS 2012-based NPP: variantsSlide20
Dealing with uncertainty
Policy managers won’t like youCost analysis of errorsOver-projections and under-projections have different costs
Wasted idle resources
vs
poorer quality of provision
These costs may be assessed differently by different people
School staff
vs educational finance officer
Developer vs resident vs planner
Political assessment of costs is necessaryThe point of considering uncertainty is to affect a planWeigh costs of over- and under-projection: affect the planContingency plans for alternative plausible predictionsSlide21
Summary
Many different planners require demographic projectionsDissemination to suit many guvnors
Some things not under the planner’s control
Predict the firm trends that all plans need to cater to
Measure the prediction’s uncertainty and declare it
Planners have responsibility
To plan
To cope with uncertaintySlide22
So what?
What could help? (collaboration/ government statistics offices/ LGA etc / LARIA / University research)Databank of indicatorsProjection scenarios
Accuracy studies
Training in demographic modelling
Authoritative research on key debates
An end to ever-smaller households: a new long-term trend or a short pause?
OAN and housing plans: creating a common language
Unattributable Population Change: monitoring the 2010s