International migration. A perspective from complexity science

Frans Willekens, Netherlands Interdisciplinary Demographic Institute (NIDI)

In this paper a perspective is proposed that explains international migration in terms of actors rather than factors or variables. The what question (“What influences migration and shapes migration flows?”) is replaced by the who question (“Who influences migration and shapes migration flows?”). Actors have traits or attributes (the variables) but more importantly, they are embedded in a multilevel context and interact with other actors, near and distant. Embeddedness and interaction (interconnectedness) are key features of the proposed perspective. It is rooted in complexity science. A complex system is a network of autonomous and heterogeneous agents at different levels of operation that interact and give rise to emergent system behaviour. The interactions usually follow simple rules and they determine how a system evolves. The challenge is to identify the agents and the rules of the game. Changes in the system are usually initiated by random events, such as technological innovations or political events. These events may be small or local. The system’s response determines its trajectory. Feedback mechanisms (adaptation) are important drivers of systems behaviour. Negative feedback is necessary to maintain the characteristics and stability of the system. Positive feedback leads to change but may also lead to system disintegration and collapse. Complexity science models complex systems from the bottom up. Aggregate patterns arise out of the interactions of agents with each other and an environment, without any central controller or other outside influence. Models that describe and predict the behaviour of a system as an outcome of actions and interactions of individual agents are known as agent-based models (ABM). A simulation of migration flows between ten countries with private and public agents illustrates the operationalization of the complexity science perspective.