This chapter defines the scope of the book's inquiry – understanding the causes and consequences of international labor migration for the global political economy. We summarize existing contributions to understanding the role of migrants in the global economy, illustrating the challenges to be taken up in the manuscript. Importantly, we discuss scope conditions, clarifying that our work, unlike much existing scholarship, does not examine political, economic, or social effects of migration on host countries.Rather, we discuss the importance of migration for sending/home countries.We provide a summary of our overarching argument – that politics matters for understanding patterns of global human mobility. Finally, we provide a plan for the rest of the book.