The literature on diffusion of knowledge has shown the positive influence of physical and cultural proximity, common language and contiguity on the speed and magnitude of international knowledge flows. Knowledge diffusion is also facilitated by co-location, even temporarily, which helps researchers form personal ties and exchange tacit information through face-to-face contact. However, the ability of researchers to disseminate the results of their work, especially recent or on-going research, through international conferences, workshop and seminar visits will be affected by the administrative barriers to mobility, for example travel visas.

This paper uses a gravity-style empirical model to examine the link between the administrative barriers to mobility, especially of the highly-skilled and students, and the magnitude and direction of international knowledge flows between 45 countries from 1990 to 2014. Additional calculations are made using information on travel visa requirements between 134 countries in 2004. The results suggest that higher administrative barriers to mobility between countries are associated with reduced bilateral knowledge flows, especially of recent knowledge, and that this effect can persist for around seven years.