The term “brain drain” was coined by the British Royal Society to refer to the exodus of scientists and technologists from the United Kingdom to the United States and Canada in the 1950s and 1960s. Now it is more typically used to refer to the emigration of a nation’s most highly skilled individuals. Rapoport and Docquier (2006) note in their entry in the New Palgrave Dictionary that it is most commonly used to denote the “migration of engineers, physicians, scientists and other very highly skilled professionals with university training”.Brain drain focuses on the so-called “high-skilled migrants”. These are migrants who have some length of tertiary (i.e. university level) education, ranging from one year of study at this level to post doctorate graduates. Statistics generally use this definition of high-skilled worker. The category of high skilled migrants is composed of three broad types:

1) Directly productive (entrepreneurs, executives, managers and technical engineers).
2) Scientific (academics, scientists and international students).
3) Health and cultural (physicians, nurses, artists, musicians, writers and media-related people).

International movements of skilled people or talent are a feature of the knowledge-based global economy. The main factors driving international mobility of high-skilled individuals (i.e. brain drain) are:
1) More favorable conditions for professional development in host countries: In destination countries, high-skilled emigrants typically earn higher salaries than in their home countries. The pay gap is such that salaries in developed destination countries are sometimes 20 times higher than in LDC countries of origin. Host countries allow higher labor productivity, due to a better industrial environment and agglomeration of knowledge workers. Moreover, destination countries offer better opportunities for professional development. In terms of career advancement prospects as well as better living conditions for emigrants and their families, superior infrastructure necessary for work and daily life and political stability. In most cases, host countries offer more favorable conditions for research and academic interaction for scientists as well as more secure property rights for entrepreneurs.
2) Adverse conditions in home countries.
3) Lower relative migration costs for the high-skilled.
4) Selective immigration policies for attracting foreign talent