1	Modeling the Causes of Urban Expansion Stephen Sheppard Solly Angel Dan Civco Williams College New York University of University Connecticut
2	Urban Expansion Widely regarded as an important policy issue Environmental impact from transportation Loss of farmland Preservation of open space Pressure for housing and infrastructure provision Policy response Land use planning Rural development Some studies of expansion in developed countries Few analyses of urban expansion in a global context
3	Data – a global sample of cities
4	Data
5	Remote Sensing
6	Measuring Urban Land Use
7	Change in urban land use: London
8	Change in urban land use: Sheffield
9	Change in urban land use: Cairo
10	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, we must have: for all locations x
11	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:
12	Modeling urban land use Finally, equilibrium requires: The model provides a solution for the extent of urban land use as a function of Population Income Agricultural land value Transportation cost If we generalize to include an export sector, then urban land use will also depend on MP of land in goods production World price of the export good
13	Testable hypotheses
14	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
15	Linear model variables
16	Linear model estimates
17	Models of change in urban land
18	Change in urban land model estimates
19	Log-linear models
20	Log-linear model estimates
21	Testable hypotheses - results
22	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
23	Conclusions and future directions Many issues to confront Endogeneity 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