Most migrants seek jobs and a better life for themselves and their families, making perceptions about "opportunity differentials" the dominant reason for migration. Some are desperate people escaping various forms of persecution or violence. And substantial numbers are people seeking to reunite with relatives. These motivations, and the availability of low-wage jobs that virtually all high-income (and increasingly, some middle-income) countries offer, induce would-be migrants to try ever more sophisticated, creative, expensive, and often riskier means to circumvent border controls and post-entry enforcement efforts -- creating a lucrative market for those who operate outside the law. The Migration Policy Institute's Transatlantic Council on Migration convened to explore how governments can meaningfully address this powerful market for illegal entry and employment. A series of Council reports published over the past few weeks delve into the migration "bad actors" that fuel and profit from illegality, examining practical policy solutions that can shrink the space in which they operate.