International migration policy for lower-income countries is still shaped by assumptions forged in an earlier era - when less-educated labor was globally abundant, skilled emigration was seen as an unmitigated 'brain drain,' and development was expected to reduce migration. That world is gone. This paper reviews a large, recent research literature on migration policy for lower-income countries in the 21st century, where demographic decline is making labor globally scarce, skilled emigration can generate net long-term gains for origin countries, and sustained development often raises (not lowers) migration pressures for generations. This recent literature suggests that migration, managed through innovative institutions, can sustain fiscal systems in aging economies, catalyze investment in human capital at the origin, and accelerate structural transformation. Managing migration is not a substitute for macroeconomic development, but a catalyst and a major opportunity. Policy priorities include building regional free movement regimes, cultivating new destination-country partnerships, restructuring skill-training systems for a mobile world, and embedding migration into aid partnerships as a core driver of development. But far more research is required on what shapes the impact of these tools.