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During a simulation, an iteration occurs every 10 years. Each city has a supply of goods and services which is produced by each urban function it fulfils, and the trade occurs till no more exchanges can be done.

1st step : Compute supply and demand :

  • Supply: depends on labour force of the city and productivity dedicated to the function at that time.

  • Demand: depends on number of inhabitants of the cities which are accessible in a given spatial range (or a network of potential customers).

2nd step : Compute trade network and trade exchanges (see Rules/Equations)

3rd step : Evaluation of residual supply after the trade exchanges

  • Any residual demand: another trade exchanges

  • No residual demand: end of the trade exchanges

4 rd step : Compute balance of exchanges then growth (see Rules/Equations)

  • Accumulation or reduction of city wealth

  • Accumulation or reduction of city population

5 rd step : Compute labor force division (see rules/equations)

  • Unsatisfied demand: increase of dedicated employees

  • Unsold production: reduction of dedicated employees

  • No more residual workers: the function is lost