1	The Causes of Urban Expansion Stephen Sheppard Shlomo Angel Daniel L. Civco Williams College New York University University of Connecticut Support from the World Bank Research Committee and the US National Science Foundation (SES-0433278) is gratefully acknowledged
2	Urban Expansion Urban expansion taking place world wide Rich Evolving from transportation choices - “car culture” Failure of planning system? Poor Rural to urban migration Urban bias? Seen as posing a variety of policy challenges Environmental impact from transportation Loss of farmland? Preservation of open space Pressure for housing and infrastructure provision Policy response Land use planning Public transport subsidies & private transport taxes Rural development Surprisingly few global studies of this global phenomenon Limited data availability
3	Data To address the lack of data, we construct a sample of urban areas The sample is representative of the global urban population in cities with population over 100,000 Random sub-sample of UN Habitat sample Stratified by region, city size and income level
4	Data – a global sample of cities
5	Remote Sensing
6	Measuring Urban Land Use
7	Data will be available for download
8	Change in urban land use
9	Display in Google Earth
10	Google Earth Ground View
11	Change in urban land use: Jaipur, India
12	Google Earth view of Jaipur
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15	Modeling urban land use Households: L households Income y Preferences v(c,q) composite good c housing q. Household located at x pays annual transportation costs In equilibrium, household optimization implies: for all locations x Housing q for consumption is produced by a housing production sector
16	Modeling urban land use Housing producers Production function H(N, l) to produce square meters of housing N = capital input, l=land input Constant returns to scale and free entry determines an equilibrium land rent function r(x) and a capital-land ratio (building density) S(x) Land value and building density decline with distance Combining the S(x) with housing demand q(x) provides a solution for the population density D(x,t,y,u) as a function of distance t and utility level u The extent of urban land use is determined by the condition:
17	Modeling urban land use Finally, equilibrium requires: The model provides a solution for the extent of urban land use as a function of We generalize the model to include an export sector and obtain comparative statics with respect to: MP of land in goods production World price of the export good
18	Hypotheses
19	Model estimation We consider three classes of models Linear models of urban land cover “Models 1-3” Linear models of the change in urban land cover “Models 4-6” Log-linear models of urban land cover “Models 7-10” Each approach has different relative merits Linear models – simplicity and sample size Change in urban land use – endogeneity Log linear – interaction and capture of non-linear impact
20	Linear model variables
21	Linear model estimates
22	Models of change in urban land
23	Change in urban land model estimates
24	Log-linear models
25	Log-linear model estimates
26	Hypotheses tested
27	Policy Implications Policies designed to limit urban expansion have tended to focus on a few variables Transportation costs and modal choice Combat “car culture” Provide mass transit alternatives Limit road building Rural to urban migration and population growth Enhance economic opportunity in rural areas Residence permits for cities Considerable urban expansion occurs naturally as a result of economic growth Limiting migration could be effective but ... Economic costs Consistency with guarantees of free mobility Regulation on use of groundwater combined with limits on infrastructure provision might prove effective
28	Conclusions and future directions Many issues to address going forward Endogeneity issues Transport costs Income Links to global economy Effectiveness of planning policies Availability of housing finance Evaluation of impacts of urban expansion In progress Field research to collect data Evaluation of classification accuracy Modeling at micro-scale – transition from non-urban to urban state Interaction with other local development