There is also a temporal dimension to a migrant's perception of distance. Today, people tend to travel greater distances than in the past. This change has come about as a result of several factors, such as improved transportation modes and communication systems.
Distance perception by people is one of the issues which have been discussed in several studies (Haggett 1965; Lowrey 1970; Briggs 1973; Lewis 1982). One of the earliest studies on distance perception stated that purely physical distance does not adequately explain interaction intensity between places, and therefore should be replaced by a new concept related to functional distance (Hägerstrand 1957). Distance tolerance is perhaps a more realistic concept than distance perception, because it accounts for not only available infrastructure and conditions to move, but also an individual's interest in moving.
As noted earlier, classic studies on migration stated that most migration occurs over a short distance. The number of migrants arriving in a given location was thought to decrease as the distance required for travel to that location increased. However, most recent studies talk about long-distance movements to global cities and the "friction" of distance has been reduced to a minimum in those cases. Long-distance migration does not diffuse uniformly throughout the whole urban hierarchical system when migration develops globally. There is a stage migration that still goes on in the lower urban hierarchy. Migrants still tend to move from one small city to a larger one, being replaced by other migrants who follow those early migrants. However, there is an increasing number of migrants who move from small cities to large global cities, avoiding a great variety of intermediate urban sites.