Global sequencing of researcher migration reveals factors associated with disparities in subnational patterns of brain gain and drain

High-skilled migration drives the global circulation of scientific talent and underpins knowledge production and innovation. Yet, internal and international migration have typically been analysed separately, leaving their combined dynamics poorly understood. Here, we present a unified global analysis of researcher migration across 1,941 subnational regions in 211 countries and territories from 2005 to 2020. Using bibliometric data as a source of digital trace data, specifically changes in author’s affiliations, from over 33 million journal articles and reviews by more than 19 million authors, we trace annual sequences of internal and international gain, drain, and stability. We identify five distinct trajectories of researcher migration that capture the evolution of brain gain and drain at subnational scales. These trajectories reveal that patterns of gain and loss coexist within many countries, including major scientific hubs, highlighting uneven internal dynamics of attraction and decline. Additionally, we explore national-level factors associated with these trends. We find that OECD membership, research and development (R&D) expenditure, and population size are the strongest correlates of these migration trajectories. By integrating internal and international migration into a unified framework, this study enables the identification and monitoring of areas where scientific capacity is expanding or declining. This evidence can be used to guide targeted interventions and spatially balanced investment in talent to reduce geographic disparities.