Migration is not a new phenomenon. The movement of populations in various forms has been part and parcel of the history of humanity. Migration has often been the cause or consequence (or both) of conflict and violence. Large migratory flows have also been driven by natural disasters, adverse climatic and weather events, and natural resource constraints.

However, there is also a fundamentally positive side to migration. Human mobility has always been an essential component of economic, social and human development and has contributed to the progress of communities and societies. United Nations Sustainable Development Goals (SDGs) recognize migration as one of the means to ensure the reduction of inequality within and among countries, in accordance with SDG 10.

People may decide to migrate for a number of different reasons. Their decisions are based on the interaction of different factors, some purely economic and others not. Under normal conditions, migration occurs in search of better employment opportunities, higher-earning jobs, and/or more and better public services, for example those related to education or health. However, in extremely fragile contexts, including prolonged conflicts and protracted crises, people may move primarily for reasons of safety and security. In reality migration decisions are complex, and choices are rarely made without constraint. For instance, when livelihoods are threatened by slow-onset events such as climate change and environmental degradation, the distinction between forced and voluntary migration may not be clear-cut. The term “survival migration” has sometimes been used to refer to migration induced by conditions of extreme economic difficulties. The important point is that in reality, migration decisions are complex and depend on multiple factors. They are best viewed as lying along a spectrum in which elements of choice and coercion intermingle and can be more or less predominant depending on circumstances and context.

As economies undergo transformation, the movement of people in search of better opportunities within and between countries is inevitable. People’s mobility is often fueled by the substantial inequalities in opportunities that persist worldwide within and between countries. Migration, being driven by these inequalities, can be an opportunity to reduce them. However, it can also represent a challenge. For example, immigrants may be viewed either favourably as a new workforce or as an unwanted burden on society, depending on whether they can be absorbed into the socio-economic system of their destination as quickly as they arrive.

Migration also represents a challenge for those who migrate – especially in terms of vulnerability at different stages of the migration process – and for the families left behind. Migration from, to or between rural areas is part of the process of structural transformation of economies, in which the relative role of agriculture in terms of income generation and employment gradually declines and labour is transferred to other sectors of the economy.

Out-migration (i.e. migrating to another community, region or country) from rural areas can also bring benefits to those areas themselves: either through the transfer of knowledge, skills and technology by returning migrants, or through remittances to migrants’ areas of origin. This can enhance human capital and support development of farm and off-farm activities as well as improve resilience to shocks. However, if out-migration occurs too rapidly, it can lead instead to a decline in agricultural production and productivity due to loss of labour, skills and knowledge and, in many cases, to the absence of labour-saving technologies.

It is clear that migrants move, internally and internationally, to seek better opportunities inside or outside agriculture. The nature and the pace of structural transformations at both origin and destination shape the trends that lead people to exit agriculture, by allocating and reallocating resources and skills across spaces and sectors.

In the last century, international migration flows have changed dramatically. For instance, Europe was a major source of out-migration, with people moving to the Americas, Australasia, and Central Asia in the beginning of the twentieth century. However, at present Europe is mostly a destination for migrants from Africa, Asia, and the Americas, as well as a locus for major internal migration flows.

In the past, transformations from agriculture-based to industry- and service-based economies have led to large-scale migration from rural to urban areas. The main drivers of this out-migration have been faster growth and higher incomes in manufacturing and associated services. However, in other contexts rural–urban migration has not been accompanied by a comparatively strong industrialization process. In the case of many countries in sub-Saharan Africa and South Asia, those migrating from rural areas to cities have mostly moved into low-productivity informal sectors such as retail trade and services, rather than the industrial sector. People leaving agriculture are not moving into industry but into low-productivity informal services or the public sector, frequently while continuing to farm as a part-time activity. While this helps rural households to deal with the seasonality of farm employment, it neither leads to complete labour transition out of agriculture nor to labour productivity gains.

Migration affects the supply of labour and the demographic composition of the remaining population as rural areas of origin risk losing the younger and most dynamic sector of their workforce and must cope with increased vulnerability of families at the source. However, migration can also contribute to agricultural and rural development in areas of origin through sending remittances which can help overcome a lack of access to credit and insurance and foster investments in agriculture or other rural economic activities as well as in human resources. They also represent an informal type of social protection intervention. Moreover, diaspora organizations and returning migrants can help rural areas through capital investment, skills and technology transfer, know-how and improved social networks.

In the decades ahead, Africa in particular will face large increases in its youth population and the associated challenge of generating jobs. Between 2015 and 2030, the combined population of Africa and Asia is projected to increase from 5.6 billion to 6.6 billion. In the same period, the number of people aged 15–24 is expected to grow by about 100 million to 1.3 billion worldwide. Almost all of that increase will take place in sub-Saharan Africa, and particularly in rural areas. With unprecedented growth in their youth populations, many of these low-income countries would face the challenge of providing decent employment for millions of new entrants in their labour markets, leading to seasonal or permanent migration.

Most of the destination countries perceive International migration, as a major challenge, with little consideration given to its potential benefits. Donald Trump’s idea of creating a physical wall across Mexico borders can be seen as one of the reflections of such perceptions.

It is a commonly held assumption among policymakers in high-income countries that economic development and rising incomes in developing countries will deter international migration. An implication is that, through official development assistance and trade policies that support development, high-income countries can supposedly contribute to reducing migratory flows from recipient countries. However, in contrary emigration generally rises with economic development until countries reach upper-middle-income status, and falls only thereafter.

The implication is that as long as inequalities and income gaps persist between geographical areas, this will lead to continuous migration from poorer regions to higher-income countries. Development in poor countries will help incomes grow, enabling people exiting poverty to cover migration costs; therefore these countries will initially see rising levels of emigration. Eventually, once countries reach a certain level of development and are able to bridge the income gaps, migration levels will start declining again.

The movement of people within and between countries is part of the process of development and structural change in economies, in which the relative role of agriculture in terms of income generation and employment gradually declines. The reallocation of economic activities across sectors and the consequent declining share of labour employed in agriculture is typically accompanied by a movement of labour from rural to urban areas, where the proportion of people has been increasing worldwide, particularly in developing regions. Today the global urban population stands at around 3.9 billion, equivalent to 54 per cent of the world’s population. This figure is expected to reach 66 per cent by 2050, compared to only 30 per cent in 1950. And migration would remain a reality in the changed scenario too.