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.