The notion of a migration system is often invoked but it is rarely clearly defined or conceptualized. De Haas has recently provided a powerful critique of the current literature highlighting some important flaws that recur through it. In particular, migration systems tend to be identified as fully formed entities, and there is no theorization as to how they come into being. Moreover, there is no explanation of how they change in time, in particular how they come to decline. The inner workings...