It’s highly concentrated in terms of destination, makes a big impact at the destinations (such as Silicon Valley) and has a large circular component. From the study published in October 2016:
The global distribution of talent is highly skewed and the resources available to countries to develop and utilize their best and brightest vary substantially. The migration of skilled workers across countries tilts the deck even further. ….
We begin by sketching the landscape of global talent mobility. The number of migrants with a tertiary degree rose nearly 130 percent from 1990 to 2010, while low skilled (primary educated) migrants increased by only 40 percent during that time. A pattern is emerging in which these high-skilled migrants are departing from a broader range of countries and heading to a narrower range of countries—in particular, the United States, the United Kingdom, Canada, and Australia. The globalization of economic ties is also leading to a rise in shorter-term and circular migration patterns for skilled labor; for example, global companies often insist that their rising executives live and work in other countries for a meaningful portion of their careers. We also give examples showing how global migration may be most pronounced for those at the very outer tail of the talent distribution and that female high-skilled migration outnumbered males in 2010.
Even among OECD destinations, the distribution of talent remains skewed. Four Anglo-Saxon countries—the United States, the United Kingdom, Canada and Australia—constitute the destination for nearly 70 percent of high-skilled migrants (to the OECD) in 2010. The United States alone has historically hosted close to half of all high-skilled migrants to the OECD and one-third of high-skilled migrants worldwide. In 2010, the United States hosted 11.4 million skilled migrants, 41 percent of the OECD total.
For recipient countries, high-skilled immigration is often linked to clusters of technology and knowledge production that are certainly important for local economies and are plausibly important at the national level. More than half of the high-skilled technology workers and entrepreneurs in Silicon Valley are foreign-born. For native workers, high-skilled immigration means both greater competition for certain jobs, but also a chance to benefit from the complementarities and agglomeration effects created by talent clusters. For sending countries, the loss of high-skilled workers raises concerns over “brain drain.”On the positive side, high-skilled emigrants can create badly needed connections to global sources of knowledge, capital, and goods—and some will eventually return home with higher social and human capital levels.
Sari Pekkala Kerr, William Kerr, Çaǧlar Özden and Christopher Parsons. Global Talent Flows, Working Paper 22715. NBER, October 2016