According to IOM, people who move voluntarily within a country are called internal migrants and move for several reasons, both formally and informally. If their movement is forced, they are referred to as internally displaced persons (IDP).
Internal movements from rural areas to urban areas is called urbanization or urban transition.
Migrants who move within the borders of their country are called internal migrants, that is, people seeking a new temporary or permanent residence, regardless of the reasons for doing so. A conservative estimate from UNDP in 2009 estimated that the global figure of internal migrants was 740 million. However, this estimate is uncertain, in part because according to the series of research on migration “International migration, internal migration, mobility and urbanization”, the greater the population of a country, the greater its percentage of internal migrants. This is also partly because of the complexity of defining the limits of this category: how far should a person be mobilized to be considered an internal migrant? How much time should they spend in this new residence? These and other questions make it difficult to measure the population that migrates within the borders of a State, and few countries keep records in this regard. Population censuses are often the most frequently used instruments to measure internal migration.
Within the category of internal migrants are internally displaced persons, who, although they do not cross an internationally recognized state border, are forced to move, “in particular as a result of or to avoid the effects of armed conflict, situations of widespread violence , violations of human rights or natural or human-caused disasters ”, as defined by the Guiding Principles of Internal Displacement.
According to the Global Internal Displacement Report 2019, in 2018, the Americas region represented 3.7% of global internal displacements due to conflict, and 9.8% of displacements due to natural disasters. This reinforces, as the report says, that internal displacement is a global challenge, but it is concentrated mainly in some countries and regions, such as Ethiopia, the Democratic Republic of Congo and Syria.
According to the UN Population and Development Commission, urbanization or urban transition is related to “a change in a population that is dispersed in small rural settlements, in which agriculture is the dominant economic activity, towards one that is it concentrates on larger and denser urban settlements characterized by a domain of industrial activities and services”. Urbanization differs from urban growth in that the former means a movement of people, and the latter refers to an increase in the urban population. The definition of what is urban and rural changes from country to country. It is relevant to note that Central America is the second highest region in the world in terms of urbanization rates and is only surpassed by Africa.
The Migration Data Portal indicates that urbanization generally occurs through processes such as natural population growth; when more people move from rural to urban areas; when the limits of what is considered urban are extended; and as a result of the creation of new urban centers. Although there are other types of internal migration flows, such as rural-to-rural, urban-to-urban, and urban-to-rural, it is the transition to the urban that has gained increased the most significantly.
Internal migrants, internally displaced persons and those who move to urban areas can be in more than one category at the same time and from there they can sometimes get confused. In addition, we must bear in mind that people come and go, adjust their residence for short or long periods of time, and therefore migration is not necessarily a linear process. Instead, it is complex and fluid and occurs in different times and spaces. The factors that promote internal migration are multiple and combine with each other. These include social, political, economic, demographic, environmental and climate issues. Internal migration can also give rise to international movements, both within the framework of forced displacement and more voluntary processes.