The Impact of Internal Migration on Urbanisation and Cities' Demographic Potential for Development in the Global South

Internal migration is a fundamental mechanism of urbanisation, yet it remains comparatively understudied relative to international migration. Beyond redistributing population across space, internal migration also reshapes the demographic structures of both sending and receiving areas. Demographic structure has direct implications for development potential through their influences on human capital, demographic dividend, and long-term population sustainability. Internal migration therefore plays a critical role in shaping development potentials. However, the extent to which internal migration alters these demographic dimensions remains insufficiently understood. This thesis addresses this gap by providing a systematic and comparative analysis of the impact of internal migration on educational composition, age structure, fertility behaviour, and demographic inequality across the Global South. It adopts the concept of urban hierarchy to capture spatial differences in development levels and migration attractiveness and examines how migration effects vary across settlement types and stages of urbanisation. The analysis draws on 103 census datasets from 46 countries, covering a wide range of development contexts. The results show that migrants are generally more highly educated and more concentrated in working ages than the populations at both origin and destination. An important exception is observed for top-tier cities, where in-migrants are less educated than local population. As a result of migration, cities tend to experience brain drain, while areas outside cities experience brain gain. At the same time, migration redistributes the demographic dividend by increasing the share of working-age population in cities and reducing it in lower-tier areas. Migrant fertility is found to be highly context dependent. Among four dominant hypotheses, disruption is universally observed around migration events, selection is most pronounced among upward migrants, adaptation is more evident among younger migrants, and socialisation is more common among older downward migrants. These patterns indicate that migration has lasting implications for fertility behaviour and long-term population dynamics. In terms of demographic inequality, educational attainment exhibits the highest levels of inequality, while age structure and fertility display comparatively lower and more stable patterns. Migration generally increases inequality, except for tertiary education, where it acts as an equalising force. Over the course of development, migration effects evolve. Top-tier cities shift from brain drain to brain gain, smaller cities experience increasing brain drain, and areas outside cities maintain brain gain. The magnitude of age-based redistribution declines in cities. Fertility disruption mechanisms shift from pure disruption to interrelation of events. Inequality decreases for higher educational attainment but increases for lower educational attainment, while remaining relat