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Europe 1300-2000

The aim of the model is :

  1. To simulate the genesis of an urban system in Europe by reconstructing the patterns of exchanges between them

  2. To test hypothesis on the role of innovation and communication speed in the emergence of hierarchical structure

Starting from the generic model SIMPOP2, we test:

  • The effectiveness of the interaction rules for differentiating size and functions of cities throughout seven centuries

  • The effect of previous geographical organization of the system on its further dynamics (path dependence) by comparing a real and a geometrical initial situation (figure 1).

- Results -

About 400 simulations have been run.

1- Estimation of historical parameters

  • Validation data
    Historical databases on population statistics have been worked out from existing ones (Bairoch and al. 1988, Moriconi-Ebrard 1994) by applying a strict methodology for comparison through time (evolutionary definitions of urban agglomerations then travel to work areas).
    From other sources, we have extracted benchmark statistics regarding urban wealth and urban functions (Maddison, Bairoch, Braudel, Mitchell, Pinol, de Vries...).

  • Key parameters
    Key parameters (productivity, demand, labour force, spatial range per function) were first roughly estimated from available sources then refined through calibration. The variations were kept consistent with principles of urban theory.

2- Calibration method

Calibration has been made iteratively across levels, on total figures (population and wealth), city size distributions, distribution of labour force, types of cities trajectories (figure 2). Major changes in key parameters have been made to reproduce the main inflexions on evolution curves :

  • Two distinct dynamical regimes (before and after Industrial Revolution) have been identified, involving two different orders of magnitude in parameter values (see Table 1)

  • General but temporary events as the Black Plague (14th century) or the pre-industrial recession (18th century) have been generated by momentary changes in key parameters.

3- Role of endogeneous and exogeneous interactions in shaping the urban system

The rules of the model are sufficient for generating the major part of cities trajectories but they fail in reproducing the specific size of the largest metropolises (table 2).

Those cities had an exceptional growth because of their "international" relationships.
This led us to inject a new function in the model, that is called world-city function. This function supplies an external demand by addressing it to other urban functions and levying part of the induced wealth. This function was revealed as a necessary ingredient of the model, as early as Middle Age (much before the general acknowledgement of "global cities"), and not only for simulating these exceptional cases in Europe but also for simulating "ordinary" urban growth in new world countries (United States).

The EUROPEAN LONG-TERM model was developed in the framework of ISCOM (European project directed by David Lane)