<Li> Threshold is the minimum market (population or income) needed to bring about the selling of a particular good or service . </Li> <Li> Range is the maximum distance consumers are prepared to travel to acquire goods - at some point the cost or inconvenience will outweigh the need for the good . </Li> <P> The result of these consumer preferences is that a system of centers of various sizes will emerge . Each center will supply particular types of goods forming levels of hierarchy . In the functional hierarchies, generalizations can be made regarding the spacing, size and function of settlements . </P> <Ol> <Li> The larger the settlements are in size, the fewer in number they will be, i.e. there are many small villages, but few large cities . </Li> <Li> The larger the settlements grow in size, the greater the distance between them, i.e. villages are usually found close together, while cities are spaced much further apart . </Li> <Li> As a settlement increases in size, the range and number of its functions will increase . </Li> <Li> As a settlement increases in size, the number of higher - order services will also increase, i.e. a greater degree of specialization occurs in the services . </Li> </Ol>

Explain the concept of central place theory in relation to world pattern of trade and transportation