Human migration is the movement by people from one place to another with the intentions of settling, permanently or temporarily in a new location. The movement is often over long distances and from one country to another, but internal migration is also possible; indeed, this is the dominant form globally. People may migrate as individuals, in family units or in large groups. A person who moves from their home to another place because of natural disaster or civil disturbance may be described as a refugee or, especially within the same country, a displaced person. A person seeking refuge from political, religious, or other forms of persecution is usually described as an asylum seeker.
Nomadic movements are normally not regarded as migrations as there is no intention to settle in the new place and because the movement is generally seasonal. Only a few nomadic people have retained this form of lifestyle in modern times. Also, the temporary movement of people for the purpose of travel, tourism, pilgrimages, or the commute is not regarded as migration, in the absence of an intention to live and settle in the visited places.
Many estimates of statistics in worldwide migration patterns exist.
The World Bank has published its Migration and Remittances Factbook annually since 2008. The International Organisation for Migration (IOM) has published a yearly World Migration Report since 1999. The United Nations Statistics Division also keeps a database on worldwide migration. Recent advances in research on migration via the Internet promise better understanding of migration patterns and migration motives.
Substantial internal migration can also take place within a country, either seasonal human migration (mainly related to agriculture and to tourism to urban places), or shifts of population into cities (urbanisation) or out of cities (suburbanisation). Studies of worldwide migration patterns, however, tend to limit their scope to international migration.
The World Bank's Migration and Remittances Factbook of 2011 lists the following estimates for the year 2010: total number of immigrants: 215.8 million or 3.2% of world population. In 2013, the percentage of international migrants worldwide increased by 33% with 59% of migrants targeting developed regions. Almost half of these migrants are women, which is one of the most significant migrant-pattern changes in the last half century. Women migrate alone or with their family members and community. Even though female migration is largely viewed as associations rather than independent migration, emerging studies argue complex and manifold reasons for this.
Often a distinction is made between voluntary and involuntary migration, or between refugees fleeing political conflict or natural disaster vs. economic or labor migration, but these distinctions are difficult to make and partially subjective, as the motivators for migration are often correlated. The World Bank's report estimates that, as of 2010, 16.3 million or 7.6% of migrants qualified as refugees. At the end of 2012, approximately 15.4 million people were refugees and persons in refugee-like situations - 87% of them found asylum in developing countries.
Structurally, there is substantial South-South and North-North migration, i.e., most emigrants from high-income O.E.C.D. countries migrate to other high-income countries, and a substantial part (estimated at 43%) of emigrants from developing countries migrate to other developing countries. The United Nations Population Fund says that "[while the North has experienced a higher absolute increase in the migrant stock since 2000 (32 million) compared to the South (25 million), the South recorded a higher growth rate. Between 2000 and 2013 the average annual rate of change of the migrant population in the developing regions (2.3%) slightly exceeded that of the developed regions (2.1%).
The top ten immigration countries are:
The top ten countries of origin are:
The top ten migration corridors worldwide are: 1. Libya–European Union 2. Mexico–United States; 3. Russia–Ukraine; 4. Ukraine–Russia; 5. Bangladesh–India; 6. Turkey–Germany; 7. Kazakhstan–Russia; 8. Russia–Kazakhstan; 9. China mainland–Hong Kong; 10. China–United States.
Remittances, i.e., funds transferred by migrant workers to their home country, form a substantial part of the economy of some countries. The top ten remittance recipients in 2010 were (estimates in billion US dollar) 1. India (55; 2.7% of GDP), 2. China (51; 0.5% of GNP), Mexico (22.6; 1.8% of GDP), Philippines (21.3; 7.8% of GDP), France (15.9; 0.5% of GDP), Germany (11.6; 0.2% of GDP), Bangladesh (11.1; 7.2% of GDP), Belgium (10.4; 1.9% of GDP), Spain (10.2; 0.7% of GDP), Nigeria (10.0; 1.9% of GDP).
The Global Commission on International Migration (GCIM), launched in 2003, published a report in 2005. International migration challenges at the global level are addressed through the Global Forum on Migration and Development and the Global Migration Group, both established in 2006.
The United Nations reported that 2014 had the highest level of forced migration on record: 59.5 million individuals, caused by "persecution, conflict, generalized violence, or human rights violations", as compared with 51.2 million in 2013 (an increase of 8.3 million) and with 37.5 million a decade prior. As of 2015 one of every 122 humans is a refugee, internally displaced, or seeking asylum. National Geographic has published 5 maps showing human migrations in progress in 2015 based on the UN report.
There are countless of reasons why immigrants choose to migrate to another country. For instance, globalization has increased the demand for workers from other countries in order to sustain national economies. Known as "economic migrants," these individuals are generally from impoverished developing countries migrating to obtain sufficient income for survival. This income is usually sent home to family members in the form of economic remittances and has become an economic staple in a number of developing countries. People also move or are forced to move as a result of conflict, human rights violations, violence, or to escape persecution. In 2013, it was estimated that around 51.2 million people fell into this category. Another reason people move is to gain access to opportunities and services or to escape extreme weather. This type of movement is usually from rural to urban areas and is known as "internal migration."  Socio-cultural and geo-historical factors also play a major role. In North Africa, for example, being an immigrant in Europe is considered a sign of social prestige. Moreover, there are many countries which were former European colonies. This means that many have relatives that live legally in Europe, who often constitute an important help for immigrants who have just arrived in a European country. Relatives might help with job research and accommodation. The geographical proximity of Africa to Europe and the long historical ties between Northern and Southern Mediterranean countries also prompt many to migrate.
There are a number of theories to explain the international flow of capital and people from one country to another.
This theory of migration states that the main reason for labor migration is wage difference between two geographic locations. These wage differences are usually linked to geographic labor demand and supply. It can be said that areas with a shortage of labor but an excess of capital have a high relative wage while areas with a high labor supply and a dearth of capital have a low relative wage. Labor tends to flow from low-wage areas to high-wage areas. Often, with this flow of labor comes changes in the sending as well as the receiving country. Neoclassical economic theory is best used to describe transnational migration, because it is not confined by international immigration laws and similar governmental regulations.
Dual labor market theory states that migration is mainly caused by pull factors in more developed countries. This theory assumes that the labor markets in these developed countries consist of two segments: the primary market, which requires high-skilled labor, and the secondary market, which is very labor-intensive requiring low-skilled workers. This theory assumes that migration from less developed countries into more developed countries is a result of a pull created by a need for labor in the developed countries in their secondary market. Migrant workers are needed to fill the lowest rung of the labor market because the native laborers do not want to do these jobs as they present a lack of mobility. This creates a need for migrant workers. Furthermore, the initial dearth in available labor pushes wages up, making migration even more enticing.
This theory states that migration flows and patterns can't be explained solely at the level of individual workers and their economic incentives, but that wider social entities must be considered as well. One such social entity is the household. Migration can be viewed as a result of risk aversion on the part of a household that has insufficient income. The household, in this case, is in need of extra capital that can be achieved through remittances sent back by family members who participate in migrant labor abroad. These remittances can also have a broader effect on the economy of the sending country as a whole as they bring in capital. Recent research has examined a decline in U.S. interstate migration from 1991 to 2011, theorizing that the reduced interstate migration is due to a decline in the geographic specificity of occupations and an increase in workers’ ability to learn about other locations before moving there, through both information technology and inexpensive travel. Other researchers find that the location-specific nature of housing is more important than moving costs in determining labour reallocation.
Relative deprivation theory states that awareness of the income difference between neighbors or other households in the migrant-sending community is an important factor in migration. The incentive to migrate is a lot higher in areas that have a high level of economic inequality. In the short run, remittances may increase inequality, but in the long run, they may actually decrease it. There are two stages of migration for a worker: first, they invest in human capital formation, and then they try to capitalize on their investments. In this way, successful migrants may use their new capital to provide for better schooling for their children and better homes for their families. Successful high-skilled emigrants may serve as an example for neighbors and potential migrants who hope to achieve that level of success.
World systems theory looks at migration from a global perspective. It explains that interaction between different societies can be an important factor in social change within societies. Trade with one country, which causes economic decline in another, may create incentive to migrate to a country with a more vibrant economy. It can be argued that even after decolonization, the economic dependence of former colonies still remains on mother countries. This view of international trade is controversial, however, and some argue that free trade can actually reduce migration between developing and developed countries. It can be argued that the developed countries import labor-intensive goods, which causes an increase in employment of unskilled workers in the less developed countries, decreasing the outflow of migrant workers. The export of capital-intensive goods from rich countries to poor countries also equalizes income and employment conditions, thus also slowing migration. In either direction, this theory can be used to explain migration between countries that are geographically far apart.
Old migration theories are generally embedded in geography, sociology or economics. They explain migration in specific periods and spaces. In fact, Osmosis theory explains the whole phenomenon of human migration. Based on the history of human migration, Djelti (2017a) studies the evolution of its natural determinants. According to him, human migration is divided into two main types: the simple migration and the complicated one. The simple migration is divided, in its turn, into diffusion, stabilisation and concentration periods. During these periods, water availability, adequate climate, security and population density represent the natural determinants of human migration. For the complicated migration, it is characterised by the speedy evolution and the emergence of new sub-determinants notably earning, unemployment, networks and migration policies. Osmosis theory (Djelti, 2017b) explains analogically human migration by the biophysical phenomenon of osmosis. In this respect, the countries are represented by animal cells, the borders by the semipermeable membranes and the humans by ions of water. As to osmosis phenomenon, according to the theory, humans migrate from countries with less migration pressure to countries with high migration pressure. In order to measure the latter, the natural determinants of human migration replace the variables of the second principle of thermodynamics used to measure the osmotic pressure.
A number of social scientists have examined immigration from a sociological perspective, paying particular attention to how immigration affects, and is affected by, matters of race and ethnicity, as well as social structure. They have produced three main sociological perspectives: symbolic interactionism, which aims to understand migration via face-to-face interactions on a micro-level; social conflict theory examines migration through the prism of competition for power and resources; structural functionalism, based on the ideas of Émile Durkheim, examines the role of migration in fulfilling certain functions within each society, such as the decrease of despair and aimlessness and the consolidation of social networks.
More recently, as attention shifted away from countries of destination, sociologists have attempted to understand how transnationalism allows us to understand the interplay between migrants, their countries of destination, and their countries of origins. In this framework, work on social remittances by Peggy Levitt and others has led to a stronger conceptualisation of how migrants affect socio-political processes in their countries of origin.
Political scientists have put forth a number of theoretical frameworks on migration, offering different perspectives on processes of security, citizenship, and international relations. The political importance of diasporas has also become a growing field of interest, as scholars examine questions of diaspora activism, state-diaspora relations, out-of-country voting processes, and states' soft power strategies. In this field, the majority of work has focused on immigration politics, viewing migration from the perspective of the country of destination. With regard to emigration processes, political scientists have expanded on Albert Hirschman's framework on 'voice' vs. 'exit' to discuss how emigration affects the politics within the countries of origin.
Lee's laws divide factors causing migrations into two groups of factors: push and pull factors. Push factors are things that are unfavourable about the area that one lives in, and pull factors are things that attract one to another area.
See also article by Gürkan Çelik, in Turkish Review: Turkey Pulls, The Netherlands Pushes? An increasing number of Turks, the Netherlands’ largest ethnic minority, are beginning to return to Turkey, taking with them the education and skills they have acquired abroad, as the Netherlands faces challenges from economic difficulties, social tension and increasingly powerful far-right parties. At the same time Turkey’s political, social and economic conditions have been improving, making returning home all the more appealing for Turks at large. (pp. 94–99)
The modern field of climate history suggests that the successive waves of Eurasian nomadic movement throughout history have had their origins in climatic cycles, which have expanded or contracted pastureland in Central Asia, especially Mongolia and to its west the Altai. People were displaced from their home ground by other tribes trying to find land that could be grazed by essential flocks, each group pushing the next further to the south and west, into the highlands of Anatolia, the Pannonian Plain, into Mesopotamia, or southwards, into the rich pastures of China. Bogumil Terminski uses the term "migratory domino effect" to describe this process in the context of Sea People invasion.