Subcenters in the Los Angeles region

1
Subcenters in the Los Angeles region

• Genevieve Giuliano
• Kenneth Small
• Presented by
  Kemeng Li

2
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
• 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

3
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.

4
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

5
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.

6
Locations of Employment Centers
7
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 cores average
  density, 29 employee/acre is higher than most
  other centers. Downtown Los Angeles, with just
  over one-half percent of the regions land area,
  contains 10 percent of jobs within the region and
  31 percent of all job within centers.
• The regions overall employment pattern is a
  dense center surrounded by areas of gradually
  declining density. Centers distance from the
  highest density zone of downtown LA is strongly
  correlated with employment density.

8
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 regions total.
  (While the centers area accouts 3 of the
  regions total). Employment-population ratio are
  surprisingly low, even in the main center. The
  average employment-population ratio for all
  centers is 1.55, less than four times the average
  for the entire region.

9
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.

10
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.

11
Cluster Analysis Result
12
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.

13
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.