Fourth, as growing proportion of migrants is now coming from the poorest parts of
the world, many developed country governments see immigration and imports as
substitutes to some extent – more economic gains in relaxing imports and political gains
in limiting immigration. Trade is thus seen as national and essentially economic matter,
while immigration is seen as local and essentially social issue (Greenaway and Nelson,
2006, p. 25). Immigration is also viewed as a national security issue in many developed
countries[14]. Fifth, trade is based on the principle of comparative advantage, while
migration is based largely on the principle of absolute advantage – to many rich
countries, immigration is more of a one-way street than trade. Moreover, the largest
gains from migration accrue to migrants themselves – but those who stand to gain are
not part of the political process in the receiving country, at least ex ante (Martin and
Mattoo, 2011).