National versus local National versus local projectionsprojections

Keith WoodheadUnderstanding Local Population Projections

SW Observatory8th September 2010

Why project?Why project? Short to medium term projections (time horizon <10

yrs) detailed forecasts for service planning & delivery

Longer term projections (10-25 yrs) strategic planning applications (eg LDF Core Strategies & long term infrastructure investment)

Long range scenarios (typically up to 30-40 yrs) exploring possible future policy contexts or to test robustness of existing plans (eg impacts of climate change on infrastructure, rising energy costs on travel behaviour)

But also Population Projections as technical inputs to other

models eg to help estimate household demand and labour supply components of economic forecasts/ projections or household trip behaviour in transport models

What does ONS provide?What does ONS provide? National projections – every 2 years – latest (2008 based) published Oct2009,

variant projections Nov ‘09) single projection years 2008-33 (5 yrly 2036-56, selected yrs to 2083), 1 and 5 yr age cohorts details http://www.statistics.gov.uk/downloads/theme_population/NPP2008/NatPopProj2008.pdf

Sub national projections – every two years – latest (2008 based) published May 2010, 5yr age groups by GOR, LA, SHA, PCOs* by single years to 2033 http://www.statistics.gov.uk/downloads/theme_population/snpp-2008/InteractivePDF_2008-basedSNPP.pdf

‘Spin-off’ projections:DCLG Household projections –trail the sub natl ONS projection by c 6

months; covers GORs, LAs; 2008 based expected Oct/Nov 2010 http://www.communities.gov.uk/publications/corporate/statistics/2026households0208

ONS Labour force projections – occasional, last publ Jan 2006 (2004 based) http://www.statistics.gov.uk/articles/nojournal/labour_force_projections_06-20/projections_fullreport.pdf

AND don’t forget, lastest updates accessible via the SWO help page: http://www.swo.org.uk/resources/data-releases/population/

* PCO = Primary Care Organisation (yes, I had to look it up too)

So, with all this ONS material, why So, with all this ONS material, why do we need local projections?do we need local projections?

Austerity Government

CSR10 -25%£

Local Projections?

Bah! Humbug

DCLG

National v localNational v localprojectionsprojections National beats local

Consistency of assumptions between areas

Subject to national peer review Adds to a generally reliable regional/ national total Avoids most local policy ‘optimism bias’

• Local beats national Reflects local knowledge, particularly impact of local migration,

development proposals, local policy change ‘Hands on’ use for testing policy scenarios etc & sensitivity

testing and can be tailored for local decision making Can be more accurate over short to medium term, but not

necessarily in aggregate (‘optimism bias’ problem)Conclusion: The two sources are

complementary and can ultimately help save resources