The Burgess model describes the patterns of land use in cities with concentric zones expanding outward from the center. The center zone (CBD) is the oldest part of the city containing commercial areas. The transition zone immediately outside the CBD is mixed-use and undergoing renewal. The inner city zone further out typically contains older terraced housing and some industry. The inner and outer suburbs zones contain newer housing, parks, and other amenities spreading to the edges of the city. The model assumes socio-economic status decreases with distance from the CBD.