Introduction: International migration - especially of high-skilled, high-educated people - is on the rise. Accordingly, academic scholars have made efforts and great progress in better understanding the patterns of migration flows across countries and their composition and characteristics - for instance, skills and gender composition. In a similar vein, governments in high-income countries have become increasingly aware of the importance of attracting skilled labor abroad to tackle skills’ shortages and scant entrepreneurial talent. Indeed, research has documented that high-skilled immigrants make a strong contribution to their host economies (see Chapter 6). As a result, many governments have introduced selective immigration policies to increase the inward flows of knowledge workers. On their side, many sending economies - not necessarily only developing countries (EU and OECD 2016) - are struggling to retain their highly trained human capital. Further evidence on what attracts and retains knowledge workers is therefore required. This chapter contributes to the literature by studying the causes of international migration and, in particular, the determinants of the international mobility of knowledge workers, which is still an underdeveloped research avenue (Brücker et al. 2012; Ortega and Peri 2013). We make use of the original data set on migrant inventors described in detail in Chapter 4 as a proxy for knowledge workers and study their migration patterns over a long period of time. We first investigate whether knowledge migration patterns and trends can be studied within the same framework that has been applied to the international migration of all workers. To achieve this goal, we make use of the well-known gravity model of international migration (for a recent survey, see Beine et al. 2016). The theoretical foundations for the gravity approach come from Roy (1951), Sjaastad (1962), and Borjas (1987, 1989), who all build different models that formalize the decision to migrate as a function of income differentials between origin and destination economies, net of the costs of moving to another country. Recent data availability on a dyadic basis (origin-destination countries) - as commented on in Chapter 2 - has allowed researchers to empirically test these and other ideas and identify the push and pull factors of international migration.< Réduire