Schelling Model

The Schelling model is the canonical agent-based model of segregation, devised by economist Thomas Schelling in 1971. Agents of two types occupy a grid and move if the fraction of same-type neighbors falls below a tolerance threshold. The striking result: even mildly preferential agents — those comfortable with up to 50% different neighbors — produce sharply segregated neighborhoods that no agent wanted. The macro-pattern is more extreme than the micro-preference.

The Schelling model demonstrates that unintended aggregate structure is not a failure of individual reasoning but an emergent property of interaction topology. It has been extended to include economic constraints, social networks, and multi-type populations, and it remains the first model complexity scientists teach to disabuse students of the intuition that outcomes match intentions.

The model also raises the deeper question of whether observed segregation in real cities is driven by preferences, by economic sorting, or by institutional bias — a question the original model does not resolve but makes unavoidable.