Transportation networks can be a factor of concentration. In the above figure, a transportation network links five locations: one hub and four feeders. Without trade, each location has the same importance. With trade, a process of geographical concentration becomes possible, which results in the development of a simple hierarchy consisting of two tiers. The hub location may see the convergence of flows and thus see its importance increase, while the feeder locations may experience a relative decline. Such a process has impacted many urban systems, as the largest cities, due to their location, grew faster than small and medium-sized centers. In addition to being a factor of concentration, transportation can be a factor of specialization.