Migration usually occurs from countries where there are excess of skilled labour to countries which have scarce human capital. For several countries, remittance is one of the major sources of income for the country. As per the World Bank Database, Bangladesh received 8.7% of its GDP in the form of remittance, Bosnia and Herzegovina received 11.7%, El Salvador received 16.8% and Jamaica received 16.3% of its GD in the form of remittances. World Bank Database shows that net migration into the developed countries have mostly remained positive over the past 5 years. The United States has a net migration of 5,007,887; the UK has a net migration of 900,000 while the UAE has a net migration of 405,000. The developing countries on the other hand harbour a different scene. The net migration over the past five years in India has been -2,598,218; from China it is -1,800,000 and from El Salvador it has been -240,415. These form a huge chunk of the population of both the countries from where the population migrates and to where the population migrates.
In the Harris-Todaro model of migration, if one assumes that the migration aspirants have the necessarily ability to migrate internationally, the trend of migration would be similar to the internal migration. The reasons for international migration are similar to the reasons of internal migration. The migrants aspire a better wage, a better quality of life and better access to other facilities due to which they migrate to more developed countries (Ukrmap, 2009).
A major problem however, with international migration is the problem of refugees. The motivation for this is political unrest or environmental issues. Wars often force people to migrate to neighboring countries in search of better political systems. As a result the amount of migration in war-struck countries has been historically high. Egypt for instance has had a political turmoil in the past few years due to which its immigration has been highly negative (-215,681). During the years when the USA had invaded Iraq, the net migration from Iraq had been constantly negative (-266320 in 1998-2002, -457332 in 2003-2007). With the advent of ISIS, the net migration from Syria has been -4029996 in 2008-2012 whereas it was positive to the magnitude of 370000 in the previous half-decade.
Thus, the above discussion shows that external migration is not only governed by economic aspirations but also by the incidences of war and political instability. The incidence of international migration is usually more complicated than internal migration because labor is not allowed to flow freely across borders. In the cases where external labor flow is free, abors migrate from one country to another in search of better living opportunities. This situation is similar to the case of internal migration. In the cases when free-flow of labor is not allowed, the migration is usually restricted to more-skilled labor or those sections of labor which have the ability to overcome the barriers, whether skilled or unskilled. Internal migration is more simplistic in nature mainly because labor flows freely from one place to another.