11.522: UIS Research Seminar (Fall 2015) - Discussion notes

Monday, October 5th, 2015, 6-8 PM

Studying the Linkage between Local Labor Markets, Urban Form and Social Stratification

Discussion Leader: Roberto Ponce-Lopez

 

According to theories of urban economics, economies of scale lie as the foundational element of cities. Economic actors benefit from agglomerating altogether in a dense urban space, such benefits are expressed as gains in productivity and reductions in transportation costs. These economic and agglomerative forces are continuously shaping the urban form through flows of people and goods traveling across local geographies. People travel from residential locations to jobs and places of consumption. This spatial interaction process exhibits a labor and consumer market geographically anchored across the city. A snapshot of the spatial layout of such markets is available by looking at census data and detailed travel records of people and goods.

The interaction between urban form and local markets is a two way influence. Urban form also shapes market interactions, affecting the emergence and location of activity centers, land consumption, and travel to places that agglomerate work and consumption. Likewise, planners can get to affect local labor markets though their influence on urban form. Bertaud (reading #1) claims that urban planners have three tools at disposal to affect urban form, which are land use regulation, infrastructure investment, and taxation.

Bertaud's reading discusses the implications of monocentric and polycentric urban forms for land consumption, housing prices, population density and travel flows. He identifies the center of activity, or what he defines as the center of gravity, analyzing the density gradients for a variety of cities worldwide. Then, he uses this measure to compare various degrees of monocentricity along its consequences on urban poverty and pollution.   

Bertaud’s methodology falls short in identifying the location of multiple centers in a polycentric structure. A more dynamic approach to localize places of attraction would be to look at flows of people. This is what Zhong, Müller, Huang and Schmitt (reading #2) do, by looking at three transportation surveys in Singapore. The authors built a measure of centrality based on the density of trips and the diversity of activities performed at each travel destination. This measure is able to capture the polycentric structure of Singapore, identifying four other regional centers of activity additional to the CBD, as they change over time.

Measures of centrality based on either population density or trips are good in recognizing the spatial structure of the city, while identifying clusters of production and consumption. However, they fail to exhibit the spatial structure of local labor markets. In other words, they do not differentiate between centers of production by type of industry, and centers of consumption by type of occupation-income. Lambert and Birkin (reading #3) propose a microsimulation analysis to build a synthetic population to identify local concentrations of employment to characterize the local labor market, which enables an exploration of the spatial dimension of social segmentation in the city. However, this approach lacks a dynamic structure to know where workers travel besides their place of work.

Putting the three readings together: an exploration of urban form, plus travel data at the individual level, plus a synthetic population localizing place of work, residence, and type of occupation, it might altogether let us to identify different clusters of production by industry type and clusters of consumption by type of occupation. This information would enable the study of the social stratification of urban space by places of work, residence and consumption. For instance, a center of production for certain type of workers could be a center of consumption to other types. In contrast, some other centers clusters of consumption and production might mix people from different income groups. This information and methods put together would facilitate the study of the spatial dimension of social segmentation of the urban space.

 

Readings:

1.     Bertaud, Alain. "The spatial organization of cities." Deliberate Outcome or Unforeseen Consequence, Background Paper to World Development Report (2003).

2.    Zhong, Chen, Stefan Müller Arisona, Xianfeng Huang, and Gerhard Schmitt. "Identifying spatial structure of urban functional centers using travel survey data: a case study of Singapore." In Proceedings of The First ACM SIGSPATIAL International Workshop on Computational Models of Place, pp. 28-33 (2013).

3.    Lambert, Paul, and Mark Birkin. "Occupation, education and social inequalities: a case study linking survey data sources to an urban microsimulation analysis." In Employment Location in Cities and Regions, pp. 203-222. Springer Berlin Heidelberg (2013).

 

Supplemental Readings:

 

Discussion Questions:

1.    Bertaud considers three aspects of urban spatial structures: the pattern of daily trips, the average built-up density, and density gradient. What other variables/data do you think might also reveal the urban spatial structure?

2.    How new technology (e.g. sensors) could improve the measurement of spatial structures?

3.    How new technology (e.g. autonomous vehicles) could modify the urban spatial structure?

4.    How different the spatial structure of Singapore would be if its structure had been influenced exclusively by the market, without intervention from planning agencies? Still monocentric? Polycentric but with a different spatial location of the centers?

5.    What local labor markets can tell us about the social segmentation of urban space?

6.    In which other ways social segmentation and segregation get visible throughout the urban space or urban form?