Urbanization continues apace at the global scale and in countries of all types cities continue to expand and to serve as the nexus of economic and social life.Within most developed countries,however,population increase occurs in parallel with decline;while some cities and regions expand,others become smaller by the year.This juxtaposition is visible in countries with stable or declining populations,such as Germany,but also in those still experiencing overall growth,such as the United States.Although an emerging body of research on urban shrinkage exists(mainly in the field of planning),less is known about the generalizable characteristics shrinking cities may share.This paper addresses the demographic components of population change associated with various urban population outcomes and offers some preliminary thoughts regarding the spatial or geographical aspects of observed decline.The data used are for United States metropolitan areas,2000 to 2010.The emphasis is on identifying types of cities experiencing population decline in such a way that resulting classifications can be applied to other settings.