Le modèle Sugarscape
Environnement
Mécanismes
Like Schelling, we have entities who live on 2 Dimensional grid. These entities have heterogeneous attributes : vision, metabolism, location, etc.
At each step, sugar grow on each cell on this grid. Each cell is limited on sugar. Dark yellow cells contain lot of sugar, and light yellow cells contain less sugar.
When the simulation start, we assign random attributes (vision, sugar in pocket, lifetime, metabolism) and random location for each people.
At each step, each creature search in its field vision the cells which contain the most sugar. If creature found such a place, she move to the place, and take the sugar.
Each step the creature eat part of sugar stored in her pocket, this is linked to metabolism, which is randomly fixed value when she born.
Creature have a limited random life. She also die when sugar in pocket equal zero.
Résultats
Starting from an homogeneous distribution of wealth into population, the simulation show a final distribution with inequalities. A minority of people has a majority of wealth, and a majority of people has a minority of wealth.
On this graphic we could observe the Carying Capacity concept. The population decreases because the sugar available into the environnement is not sufficient to feed all the people.
We also observe the path dependencies concept, by evolution the system promotes the people with good vision, and low metabolism. If you are blind and you consum lot of sugar to survive, life will be very difficult for you in this model.
These concept also exist to qualify urban system.
We now add new rules to illustrate the Resilience concept.
We introduce two category of people in the model, the farm workers, and the farm owners. Farm workers continue recolt the sugar like the initial model, but the far owners cannot recolt the sugar.
It’s a master slave relation, farm workers pay a tax to farm owners at each step of simulation. If the tax is too high, slave have no food and cannot survive. But if slave die, master also die.
Farmer could also reproduce with 5 sugar if they have more than 40 sugar in pocket. Children appear randomly on the map.