Transcript Subcenters
Subcenters in the Los Angeles region Genevieve Giuliano & Kenneth Small Presented by Kemeng Li Introductions and Objectives • • • • Metropolitan areas are now characterized by decentralized patterns of employment rather than by monocentric urban structure. Subcenters are generated when the congestion effects are high and agglomerative forces are strong. This paper presents an empirical analysis of employment and population patterns of subcenters in the Los Angeles region. The three objectives of this paper are 1. 2. 3. To develop a method for systematically identifying employment subcenters To Apply the method to the data from Los Angeles region To analyze the functions and distribution of centers Data and Study Area • The study region covers the urban portions of Los Angeles, Orange, Ventura, Riverside and San Bernardino Counties, an area with 3,536 square miles land, 10.7 million people and 4.65 million jobs. • The area was divided into 1146 ‘transportation analysis zones’ defined by Southern California Association of Governments. • The 1980 Census data provide information on population characteristics, employment, and travel flows at spatial detail. Definition and identification of subcenters • Among various ways to define subcenters, this paper agree with McDonald(1987)’s that employment, not population is the key to understanding the formation of urban centers; and that a center is best identified by finding a zone for which gross employment density exceeds that of its neighbors. • A center is therefore defined as a continuous set of zones, each with employment density above some cutoff D, that together have at least E total employment and for which all the immediately adjacent zones outside the subcenter have density below D • Density cut-off D is chosen to be 10 employees per acre, minimum total employee E is chosen to be 10,000 Identification of subcenters and their characteristics • Using these criteria, this paper identify 32 centers (listed in table1) • The four largest centers form an arc from Santa Monica through downtown Los Angeles, which we call the Wilshire Corridor. These four plus one smaller subcenter (No22) would form one giant center, 19 miles long. We call these five centers together the core. Locations of Employment Centers Findings about subcenters • Dominance of the core centers ----The five centers in the core contain more tan half of all jobs located in centers. The core’s average density, 29 employee/acre is higher than most other centers. Downtown Los Angeles, with just over one-half percent of the region’s land area, contains 10 percent of jobs within the region and 31 percent of all job within centers. • The region’s overall employment pattern is a dense center surrounded by areas of gradually declining density. Center’s distance from the highest density zone of downtown LA is strongly correlated with employment density. Findings about subcenters • Table 3 shows the distributions of total employment & employment density across samples of centers. We can see that the largest, densest centers tend to be close to the core. • Centers have a high concentration of population, accounting for 9 percent of the region’s total. (While the centers’ area accouts 3% of the region’s total). Employment-population ratio are surprisingly low, even in the main center. The average employmentpopulation ratio for all centers is 1.55, less than four times the average for the entire region. The functions of employment centers • We want to examine the whether the agglomeration economies generating subcenters apply only within an industry (creating a tendency for some centers to specialize) or apply to an entire complex of industries (creating centers with mixed activities) • Cluster Analysis --First, the paper classified eight industrial sectors to examine this question. Manufacturing, transportation, communication, utilities, and whole sale trade together form a group of production-oriented sectors accounting for an employment share of 41 percent, the other three sectors, all service oriented , account for 55 percent. Cluster Analysis ---The functions of employment centers • Cluster analysis is to use the 32 centers as observations and use the eight industry shares as variables. Each observation is described in terms of all the eight variables (represented by a point in a eight dimensional space). The ‘Distance’ between two centers in the eight dimensional space reflects the dissimilarity of the two centers in terms of their function. • Observations that are measured to be close to each other in the eight dimension space form a cluster. • The analysis suggest that five clusters best describe the subcenters. Shown in table 5. Cluster Analysis Result Cluster analysis---The functions of employment centers • Overall, the cluster analysis suggests that subcenters play diverse roles within the regional economy. Downtowns continue to function as administrative, service, and retail centers with substantial amounts of other industry. The specialization of centers in services, manufacturing may be indicative of spatial differentiation that occurs as regions become heavily urbanized. • The more service-oriented centers tend to be closer to the core area. The result suggest that congestion effects (including land costs) may repel production-oriented activities as the level of concentration increases. • At the same time, the four large centers in the core are in four different clusters, suggesting further that even at this level the urban system requires a variety of types of centers. Conclusion • This paper identified 32 employment subcenters in Los Angeles region using a consistent method. • We find the economic activity is heavily concentrated along a linear core area consisting 5 centers. • The cluster analysis suggests that the employment in subcenters occurs in recognizable industry-mix patterns ranging from highly specialized to diversified.