Shrinking cities  Shrinking cities or urban depopulation are dense cities that have experienced a notable population loss. Emigration (migration from a place) is a common reason for city shrinkage. Since the infrastructure of such cities was built to support a larger population, its maintenance can become a serious concern. A related phenomenon is counterurbanization. The phenomenon of shrinking cities generally refers to a metropolitan area that experiences significant population loss in a short period of time. The process is also known as counterurbanization, metropolitan deconcentration, and metropolitan turnaround. It was popularized in reference to Eastern Europe post-socialism, when old industrial regions came under Western privatization and capitalism. Shrinking cities in the United States, on the other hand, have been forming since 2006 in dense urban centers while external suburban areas continue to grow. Suburbanization in tandem with deindustrialization, human migration, and the 2008 Great Recession all contribute to origins of shrinking cities in the U.S. Scholars estimate that one in six to one in four cities worldwide are shrinking in countries with expanding economies and those with deindustrialization. However, there are some issues with the concept of shrinking cities, as it seeks to group together areas that undergo depopulation for a variety of complex reasons. These may include an aging population, shifting industries, intentional shrinkage to improve quality of life, or a transitional phase, all of which require different responses and plans. There are various theoretical explanations for the shrinking city phenomenon. Hollander et al. and Glazer cite railroads in port cities, the depreciation of national infrastructure (i.e., highways), and suburbanization as possible causes of de-urbanization. Pallagst also suggests that shrinkage is a response to deindustrialization, as jobs move from the city core to cheaper land on the periphery. This case has been observed in Detroit, where employment opportunities in the automobile industry were moved to the suburbs because of room for expansion and cheaper acreage. Bontje proposes three factors contributing to urban shrinkage, followed by one suggested by Hollander:   The shrinking of urban populations indicates a changing of economic and planning conditions of a city. Cities begin to 'shrink' from economic decline, usually resulting from war, debt, or lack of production and work force. Population decline affects a large number of communities, both communities that are far removed from and deep within large urban centers. These communities usually consist of native people and long-term residents, so the initial population is not large.