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