A suburb is an area within a metropolitan area which is predominantly residential and within commuting distance of a large city. Suburbs can have their own political or legal jurisdiction, especially in the United States, but this is not always the case, especially in the United Kingdom, where most suburbs are located within the administrative boundaries of cities. In most English-speaking countries, suburban areas are defined in contrast to central city or inner city areas, but in Australian English and South African English, suburb has become largely synonymous with what is called a "neighborhood" in the U.S. Due in part to historical trends such as white flight, some suburbs in the United States have a higher population and higher incomes than their nearby inner cities.