Diasporas, sometimes referred to as expatriates or transnational communities, play an important role in leveraging migration’s benefits for development. Measuring issues relating to diaspora groups is challenging, as there is no agreed-upon definition of "diasporas". Data on migrant stocks can act as a proxy for diaspora populations, and remittance data are also closely linked to the study of diasporas. Since the 1990s, many states have established wide-ranging programmes aimed at promoting relations with diasporas. However, differences in definitions and a lack of robust monitoring and evaluation mean that comparative analysis of these policies is difficult.