The Schelling segregation model

The phenomenon of residential segregation appears as an emerging pattern in the real world considering different segregation criteria (educational level, social religion, annual income, economic status, ethnicity, political point of view, etc). The following two websites show examples of how groups with similar characteristics tend to cluster in London:

• Inequalities in London
• Mapping Where Immigrants Settle in London, Street by Street

In 1971, the American economist Thomas Schelling created an agent-based model that might help explain why segregation is so difficult to combat. An agent represents a household. Each agent lives on a square of a 2D grid. There are two types of agents on the board. The agent follows a simple rule: if a predefined number of my neighbours are not like me, I am unsatisfied and move to a random place on the board. In the following example, a rectangle agent is satisfied when at least 30% of neighbours are like him (30% of 8 neighbours means there are 3 or more rectangles).

His model of segregation showed that even when agents did not mind being surrounded or living by agents of a different type, the segregate pattern still emerged over time. With a simple model, Schelling gives a fascinating insight at how households might self-segregate, even when they have no explicit desire to do so.