Projecting transient populations - pragmatism or technical correctness? BSPS Conference Sep 2004 Richard CooperResearch team Nottinghamshire County Council

Joint Structure Plan housing figures Regional Planning Guidance (1996-based) – 49,000 dwellings Joint Structure plan accepts total Distribution to sub-areas South Nottinghamshire = 37,000 Nottingham City – supply of 18,500

Population projections for Nottingham City Basis is a ‘set’ number of dwellings Early projections were dwelling-led but – –Migration levels varied widely –Migration-led projection needed –More robust output –More up-to-date information available City wanted age / gender projection

Knowns and unknowns How many houses – but not types of house, household or occupants Age/gender of residents and migrants – but not future migrants Characteristics of residents – but not how those may change

Modelling the population Changing housing provision (e.g. more flats) Assumptions that data in the model will still pertain - –the migration profile remains the same –characteristics (fertility, household generation, etc.) of population remain same for age, gender & relationship

Nottingham City – 2001 Census

Nottinghamshire (rest of Plan Area) – 2001 Census

Age profile of some JSP districts

Nottingham city projection – no transient population

Effects of ignoring the transient population Age structure would have many more adults 35-44, (and fewer 15-24) –ageing through fertile and household creation ages For a set number of dwellings (18,500) –8,000 fewer (30% less growth) For a certain migration level –2,500 more dwellings

But why is this a problem (to Notts!) ? Decision to use Patient Register data –From ONS & used in mid-year estimates –More up-to-date –More complete than the Census (includes students) –3 years data –More accurate?

A problem ? (2) 3,000 more net in-migrants – but are these all students?

A problem ? (3) Transient population used where migration data does not handle flows adequately (1991 Census) If migration data complete there is no need for a transient population - in theory OK However, results did not show sensible outcome – it appeared that some student migrants were being excluded

Determining a transient population Needed a reality check Thought that transient population in CPHM was wrong for application to Patient Register migration How do you decide on a transient population when some information is missing? What should the relevant (20-24) population be doing? It does not remain absolutely constant, even though student numbers may do so – so how does it change? Look at births 20 years ago, not for absolute numbers – but for trends

What the year old projectionss should be showing

Changes to yr old population Original projection has no transient adjustment May 2003 resulted from City suggestion in setting transient population Mar 2004 accounts for latest information and migration-led projection

How does it compare? (1)

How does it compare? (2) NB 1996 trend-based, so unusable for Structure Plan Methodology incorporated separate student ‘adjustment’

How does it compare? (2) Main difference is higher population in JSP