Figure 3.10.State of origin for US domestic migrants. Distance decay is evident in that people tend to move between states within the same region. Explore the data in ArcGIS Online at https://arcg.is/1ymjTa. Data source: US Census.
Go to ArcGIS Online to complete exercise 3.1: “Spatial distributions.”
Push and pull forces
As seen in the previous section, some places clearly attract immigrants, while other places induce emigration. To understand the driving forces behind these patterns, it is essential to look at the place-specific characteristics of sending and receiving locations as well as the spatial interaction that ties places together.
Different theories have been given to help explain how, where, and why people migrate. One of the first and most influential thinkers on migration was E. G. Ravenstein, who in 1885 wrote On the Laws of Migration. He presented a set of “laws” based on his research in Great Britain in the nineteenth century. While some of his laws do not apply to all contemporary migration trends, many still inform modern migration theory. Ravenstein’s laws of migration are as follows:
•Migrants move short distances along fixed currents toward “great centers of commerce and industry.”
•Rapidly growing cities absorb migrants from nearby places. The places vacated by these migrants are then filled by migrants from places farther away, in a step-by-step fashion. Communication flows between places can countervail the disadvantages of distance.
•Some places see a dispersion of their populations, as they migrate to growing urban areas.
•All migration currents have a compensating countercurrent.
•Long-distance migrants generally move to one of the great centers of commerce or industry.
•Rural residents migrate more than urban residents.
•Females migrate more than males.
Implicit in Ravenstein’s work is the idea that certain places attract immigrants, as in his “great centers of commerce and industry.” The idea that some places attract people led other migration researchers to expand on the idea of push and pull factors. These theories are based on the fact that places of origin have factors that “push” people to leave, while places of destination have factors that “pull” people to come. These forces can be viewed in terms of the economic, social and cultural, political, and environmental conditions of places.
Ravenstein also noted that migration is not random but rather is tied to currents of migration—flows between specific places that people follow in regular patterns. This spatial interaction between places is fed by communication, as people share information on the opportunities and challenges involved with making the move. Furthermore, he noted that the characteristics of migrants take a specific form. Migrants are not randomly selected from the general population but tend to have specific characteristics in terms of sex, age, income, and other variables.
Economic push and pull
As you may expect, some of the most common reasons to migrate are economic. One way of understanding how economic forces influence migration is through neoclassical migration theory. This theory focuses on wage differentials between origin and destination. If wages are low in one place relative to another place, then individuals will be pushed from the low-wage to the high-wage location. This theory is useful in understanding much migration, in that historically and globally, economic forces are the key drivers of migration.
For example, most migration from Mexico to the United States has been driven by significant wage differences between the two countries. The average Mexican income in 2014 was US $12,850, adjusted for cost of living differences with the United States. This compares to average US earnings of $57,000. But neither most Mexicans nor most Americans earn the average income. In 2014, 14.8 percent of Mexican workers earned less than two-thirds of the median wage, the equivalent of US $707 or less per month, again accounting for differences in cost of living. Those making only the minimum wage earned less than US $160 per month. By migrating to the US and earning the 2014 federal minimum wage of $7.25 per hour, a full-time worker would earn about $1,160 per month. That is a 60 to 600 percent increase in wages—certainly enough of an incentive for many to migrate. The gains are even greater for immigrants who arrive in states with minimum wages above the federal level. For instance, the 2014 minimum wage in California was $9 per hour, while in Illinois it was $8.25 and in New York, $8.
But wages alone are not enough to explain all migration patterns. Economic forces can also include unemployment rates, working conditions, and opportunities for career advancement. Places with high unemployment rates are likely to push people away, while places with low unemployment will pull people in. Similarly, a place with a cluster of large corporations in a specific industry may offer attractive benefits packages, interesting coworkers, and opportunities to move into positions of greater responsibility. The technology cluster in Silicon Valley, for instance, pulls in people from all over the US and the world for good wages but also for fun and interesting work and myriad opportunities for professional growth. Likewise, people migrate from around the world to New York and London because of ample career opportunities in their financial sectors.
The level of emigration from a place can also be related to level of economic development (figure 3.11). This relationship is described by the migration transition theory, which is closely related to the demographic transition theory discussed in chapter 2. In preindustrial societies, emigration is low. High, yet roughly equal, rates of births and deaths mean that population growth is minimal, so there is no demographic pressure to emigrate. Furthermore, because of limited income, people do not have the resources to travel to new places.
Figure 3.11.Migration transition theory. Emigration increases as countries industrialize and urbanize, but as they get richer, emigration falls. Image by author.
As countries begin to industrialize and urbanize, as in stage 2 of the demographic transition, high birth rates and falling death rates result in a population boom. Incomes also increase during this time as economies shift from basic agriculture to mechanization on farms and in factories. With population pressure and higher incomes, migration increases significantly. During this stage, there is massive rural to urban migration as people shift from agricultural work in rural areas to manufacturing work in cities. There is also emigration to other countries, as people seek new opportunities farther from home.
As countries continue to develop through urbanization and industrialization, they enter stage 3. During this stage, birth rates fall, resulting in a slowing of population growth. As population pressures decline, rural to urban migration and emigration rates slow somewhat.
Finally, modern, urban stage 4 countries with low birth and death rates, have low levels of emigration. Migration tends to be city to city, while net international migration is positive as more migrants arrive than leave.
Given that Mexico has been one of the most important sources of immigrants to the US in recent decades, it is useful to view Mexican immigration in terms of the migration transition. Figure 3.12 shows how income and fertility have changed in Mexico since 1990. Whereas in 1990 the per capita income was $5,820, by 2014 it had risen in real dollars to $17,200. At the same time, the total fertility rate had fallen from nearly 3.5 children to about 2.2. As Mexico transitions to a higher income and lower fertility country, the migration transition theory predicts that emigration will decline.
As pointed out previously, Asian immigration to the US is now higher than that from Latin America. As the economies of Asia grow, a larger number of people have the financial resources to immigrate to the United States. While birth rates in much of Asia are relatively low, the sheer number of people in the region means that a substantial number are available