In this review we will be covering topics related to migration as well previous refugee crises. Since most
migration models include refugees as a particular form of human migration under some external
pressuring factors, we will focus on the migration literature.

Modern migration theory intensified in the 1970s as a result of the involvement in far-eastern conflicts of
the United States, but it really took off with the fall of communism in Europe in the end of the 80s and
early 90s. The conflicts in Africa and as a result the intensifying refugee flow to Europe in the 2000s also
prompted researchers to look more deeply into the root causes of not only migration but also social
integration upon arrival.

Perhaps the most prominent mathematical model that is widely used for many social phenomena,
including migration is the gravity law (Zipf, 1946). Yet there are other models and theories that developed
to model the pattern of migration.