relationship between the international mobility of researchers and their performance. Finally, firm learning from diaspora has also increased sharply (Oettl and Agrawal. 2008).

# **V. Conclusions and Directions for Future Research**

As is evident from the literature review, application of international trade and FDI theories to global mobility of students and scholars is virtually nonexistent. Furthermore, lack of research on the impact of returning and non-returning international students on international knowledge diffusion needs to be addressed (King and Raghuram, 2013). Raghuram (2013) suggests that an analysis of student migration where the inducements that universities offer to prospective students and the subjective responses of such students to these invitations will throw light on how the spatiality of knowledge is achieved and highlight the distinctiveness of student migration in a skilled migrant world. Research on international students whether at the regional, national or international levels has been hampered by a lack of a comprehensive international student and scholar database. Although detailed data on international students are available to the public for at least five countries-US, Canada, Australia, the UK and Turkey, and to some extent for New Zealand and a few EU countries, they are fragmented, hampering any meaningful analysis. Furthermore, for countries such as Denmark, database on stay rates is very expensive. Discussed below are suggestions for future research on international student mobility.

_(i) Creation of an International Student Database_ There is a need to create a database on international student mobility in the context of trade in services and migration. The most detailed data are available for the United States. However, these data are from different sources such as the National Science Foundation and the Institute for International Education. Detailed data by different schools such as engineering, level of study such as PhD as well as field, university, country and nationality of professors are available from various data sources published by the NSF at the national and state levels. Birthplace of the professors are available from the faculty information of the various universities by schools and departments. In addition, stay rates of international students have been published by the Oak Ridge National Labs (Finn, 1999-2014). Such details are not available for other countries, but the UK, Australia, Turkey and Canada publish data on international students by country and fields of study such as engineering. Other countries such as New Zealand, Ireland and Japan and a number of EU countries also have some detailed data on international students.

# _(ii) Application of International Trade Theories to Trade in Education Services_

Global student mobility is an international trade in services phenomenon. The student sending country imports services, while the receiving country receives tuition and other expenses from the student and hence is the exporting country. Despite setbacks during the early post-9/11 period (2001-2006), the number of international students in the US has generally trended upwards (Bird and Turner, 2014; Niemen and Swagel, 2009; Alberts, 2007). In addition, for the host country national and sub-national 16