Classical theories developed by researchers such as Adam Smith and Karl Marx outline a model of migration based on economic push and pull factors. Push factors include lack of access to land, lack of employment and under-employment, low wages, underutilized land, drought, famine, and population increases. Pull factors comprise attractive urban alternatives for the rural dwellers, such as higher wages and better living conditions. Neoclassical theorists such as Todaro (1976, 1977) regard motivation for rural-urban migration as a function of two variables: the difference in real income between rural and urban areas, and the probability of obtaining a better-paid job in the city; this is because they believe that the rural agricultural sector is characterized by zero or very low productivity. Researchers such as Mortuza (1992) and Li (1996) propose that the most important reasons for moving to a city are underemployment and low income in rural areas, while others, such as Anzorena and Poussard (1985), Scott and Litchfield (1994), and Burgess, Carmoda, and Kolstee (1997), regard rural poverty as the main reason for leaving rural areas.
In short, both classical and neoclassical migration theorists focus on economic factors. However, both types of theory are criticized, by researchers such as Sjaastad (1962), McGee (1977), Danesh (1987), Williamson (1988), Castles and Miller (1998), Anderson, Domosh, Thrift, and Pile (2003), and Stalp (2006), for being incomplete explanations of the complex migration phenomenon. Theorists explaining the neoclassical viewpoint describe how social, political, cultural, religious, and traditional factors and migrants' links with their destination, also play a very important and decisive role. Moreover, proponents of classical and neoclassical migration theories cannot effectively explain migration in developed countries. This is because, firstly, the proponents of the two types of theory have focused only on geographic wage and price differentials--between the destination and origin--as the underlying forces in the migration process. Such factors cannot be used to explain the process of migration in developed countries, where job transfers and other reasons unrelated to the search for a higher income, cause the majority of population movements. In these cases, migrants "are not responding to geographic salary differentials, but to institutionalized organizational forces" (see also Johnson & Salt, 1990, p. 29; Kang, 1994). In other words, migrants do not respond to labor market demands and they are professional, noncompeting groups (Johnson & Salt, 1990).
Secondly, the main motivation for migration within developed countries is job transfers and other reasons not related to the search for a higher income. This differs from developing countries, where the majority of migrants move in search of a higher income as a result of push and pull factors in both places of destination and origin. In other words, it is reasonable to say that the motivation for migration in developed countries is not strongly influenced, not by economic factors or economic necessity, but rather by migrants' responses to other factors. This is the biggest difference in comparison with developing countries, where the motivation for migration is often strongly influenced by economic necessity.
There are two main reasons for this. The first is that the differences in wages and living conditions between rural and urban areas of developed countries have become marginal or insignificant. At the same time, the populations of both the places of origin (rural) and destination (urban) have similar access to services and facilities that are only available in urban areas in developing countries. Therefore, migration from rural to urban areas is unlikely to be motivated by the search for a higher income or better living conditions, since urban areas and especially large metropolitan areas are often …