Urban and regional studies begin with analyzing the spatial structure, particularly population density patterns. As population serves as both supply (labor) and demand (consumers) in an economic system, the distribution of population represents that of economic activities. Analysis of changing population distribution patterns is a starting point for examining economic development patterns in a city or region. Urban and regional density patterns mirror each other: the
central business district
(CBD) is the center of a city, whereas the whole city itself is the center of a region, and densities decline with distances both from the CBD in a city and from the central city in a region. While the theoretical foundations for declining urban and regional density patterns are different (see Section 6.1), the methods for empirical studies are similar and closely related.