In general, countries' urban populations are defined as the residents whose main source of income is not from agriculture or forestry (Satterthwaite, 2010). Urban population projections often do not include high- and low-variant estimations, which are typical of world population projections published by the United Nations (Satterthwaite, 2007; United Nations, Department of Economic and Social Affairs, Population Division, 2012). Moreover, the traditional urban/rural dichotomy has become increasingly inadequate for distinguishing between urban and rural settlements.