Population Forecasts – The outline model

In what may turn out to be a rash and dreadfully overoptimistic move, we have decided to build a local population forecasting model for Bath and North East Somerset, here’s how we’re going about it:

We have liberally borrowed from the ONS Sub-National population projections and added an additional component to look at new housing growth.

We also took some advice from our good friends at the University of Bath who have been able to give some pointers and suggestions.

The outline methodology, as it stands looks something like this:

Stage	Activity
Determine baseline	Choose a date! Choose a spatial area Choose demographic variables to forecast
Remove static population	Students Care homes Armed forces What else?
Age-on remaining population
Natural Change	+Births Estimates – Deaths estimates
Adjust for migration	Mid-year population estimates Constrain to census for small area? Do we have any internal (in B&NES) models – e.g. council tax Do we need to account for external factors Develop historic models to test assumptions
Add new households (Market)	Create nominal household occupancy rate + proportions at single year of age Develop historic models to build and test assumptions Determine household nos. Apply single year occupancy rate to households
Add new households (HMO/Care Homes)	Identify planning permissions with occupancy rates Add resident per bed by single year of age and add to static population (and add for future years)
Add static population back in
Constrain	Determine factors and data sources e.g. planning over-optimism, migration?

Our next blog will look at these components in more detail and define some of the data sources we’ll need to use.

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