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Modelling & training > Our suite of economic models > IPM: Integrated spatial policy model

IPM: Integrated spatial policy model

Motivation

The IPM model is intended to support strategic decision making for spatial economic strategy and planning.
The model seeks to represent the key features of economic geography that until now have typically been found only in theoretical models.
It has been designed to address the following weaknesses in traditional approaches:

• projections of, on the one hand, the scale and location of population and, on the other, the scale and location of employment, are made independently of one another, or with little attempt to capture the important links between them; the result is that, for example, housing strategy is developed without taking account of the scale and location of the jobs where people will work
• economic and demographic projections for areas pay little or no attention to economic geography, and in particular to the spillover effects from one area to another (for example, provision of housing in one area increases the supply of labour available to work in another area which is within commuting range)
• transport and land-use models seek to capture these effects, because they are critical to an understanding of how many trips will be generated, but the focus in such models is on the detailed demands that will be placed on the transport network; such models typically either take the location of population and employment as given, or are implemented in great detail for a particular travel-to-work area and not suitable for developing spatial and economic strategy

Distinctive features of the IPM approach

• the IPM determines the location of population and employment simultaneously, with the results for one area determined by, and having an influence on, the results for 'neighbouring' areas, where 'neighbouring' is measured with reference to travel time
• its 'neighbourhood' effects include:
  • the link between the availability of labour supply for employment in locations to which commuting is feasible and the location of housing
  • the demand for local goods and services (notably for public services and retailing)
  • the 'cluster' benefits of co-location
• it incorporates a concept of economic distance which depends on the transport network, but does not duplicate the detailed trip generation modelling of transport models
• it takes as assumptions the availability of property space and the travel time between areas; the user can then vary these assumptions to simulate the effects of policy interventions; it does not assume that land released for development will necessarily be developed; rather, it models the take-up of available space

Scope

Currently the model is designed to be implemented for any single NUTS1 area of the UK, distinguishing

• the region's local authority areas as the spatial unit
• jobs and value added by industry sector
• workers by broad occupation
• population by broad age group
• housing and commercial property requirements

The first application of the IPM was developed in cooperation with the West Midlands Regional Observatory whose website has further information.