Human Capital Flight from Iran

In recent days; President of Iran has invited Iranians abroad to invest in their mother land and made a firm pledge of government's steely determination to coordinate with the Parliament and other branches to facilitate their return. Not only the return of capital but also return of human capital and highly-educated individuals is of crucial importance.
In 2013, 9000 Iranian university students studied in the United States; with an estimated 80% of postgraduates. Unfortunately there is no exact figure but the numbers are certainly higher than that.
To address the issue; we pose two questions:
- What are the specialties of Iranian academic elite abroad? Does their return signal far-reaching changes in the country?
- What are the prerequisites to that?
In hopes of future prosperity for Iran