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I work on urbanization in developing countries and in my recent research I have looked at the spatial patterns of
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urbanization in India trying to understand the economic implications of different city structures and more
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specifically I've looked at one particular property of urban footprints which is their geometry if you look at
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urban areas from a plane for example you can see that cities become in different
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shapes some have outlines that are roughly circular others appear more fragmented and yet others are
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constrained by their geographies for instance cities on islands or peninsulas end up having even more irregular shapes
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so my question was what influence if any does a cities shape have on the location
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choices of consumers and firms do consumers and firms benefit in terms of welfare or productivity from locating in
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cities with particular shapes now why would we expect City shape to matter at all from an economic standpoint
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primarily because as urban planners have long recognized City shape is one of the
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determinants of urban commuting efficiency along with more widely studied factors such as infrastructure
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or travel demand and the reason is that more compact more circular city geometries are conducive to shorter
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within city trips to give you a sense of how this works this is just coming from
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the properties of geometric shapes think of a circle and now imagine that holding
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area constant you start tweaking the circle turning it into some irregular shape as the shape of this polygon
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departs from that of a circle becoming less and less compact the average distance between points within this
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polygon will tend to increase and the same thing happens to cities as they expand in space
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a good real-world example of these types of interactions is the comparison between kolkata and bangalore of the top
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cities in india kolkata is the least compact one it kind of looks like an upside down giraffe head with a long
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north-south tentacle so to say bangalore on the other hand is more like a pentagon it's the most compact one i
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calculate that all else being equal if kolkata had the same compact shape that bangalore has the average within city
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trip proxied by the average distance between points within the city would be shorter by six point two kilometers and
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this is not trivial if you think that the average commuting speed in the top cities in india is around 15 kilometers
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per hour so what i did was to look at the outlines of over 450 cities in india based on how they appear in nighttime
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satellite imagery if you look at a picture of the earth at night taken from a satellite urban areas are clearly
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visible as patches of light essentially so for each city for each of these patches of light i computed a number of
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indicators for geometric shape that are basically telling us the extent to which
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a city's shape departs from that of a circle and I did this for multiple years
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to have a sense of the dynamic evolution of City shapes over time and finally I linked City shape to economic outcomes
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measured at the city level such as population aggregate look sorry average local wages and average housing rents
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so I find that households locating in more compact cities are better off first more compact cities attract larger
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populations second households that are located in more compact cities are implicitly paying a premium in terms of
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higher housing rents net of local wages in order to live in cities with better geometries so this tells us that
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essentially consumers are valuing City compactness as an urban amenity that they are willing to implicitly pay for
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in this implied premium that they are paying is actually quite large i estimate that households are trading off
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implicitly five percent of their income in order to live in cities that are more
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compact by one standard deviation now for the average City a one standard deviation improvement in compactness
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implies that your average round-trip commute decreases by 720 meters these are potential commutes estimated based
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on the distribution of points within the city these are not observed commutes which unfortunately I can't see in my
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data on the other hand firms are not affected in their productivity by City shape compact compact cities are just as
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productive and compactness appears to be a pure consumption amenity now you may worry that compact cities are
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systematically different from others in some dimension other than geometry what if these more compact cities are also
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more successful more developed cities that consumers like for reasons that are just correlated with geometry but have
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nothing to do with it to address the fact that these confounding factors might be biasing my results in my
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analysis I'm not simply making a crude comparison between compact and non compact cities what I do is look at what
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happens when a given City becomes less compact as a result of hitting some topographic obstacle like a mountain or
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a lake as it expands in space and what I find is that when a city ends up with the worst geometry because of hitting
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some geographic constraints its population growth slows down and housing rents net of local wages tend to
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decrease well India's predicted to urbanize very rapidly in the next decades and local
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policymakers need options to accommodate this urban growth in space and my findings suggest that accommodating this
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urban expansion in a more or less compact way can have potentially relevant implications for household
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welfare and for urbanization patterns now clearly not all cities can be circular due to topography and in fact
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at a descriptive level one of the patterns that I find is that cities tend to become less and less compact over
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time as they expand but there is room for land use regulations to promote more or less compact development and as an
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example of this in my work I consider a regulatory tool that is considered quite
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controversial in India right now vertical limits restrictions on building heights that in India are considered
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very strict relative to international standards and a lot of commentators and local policymakers are concerned that
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these stringent vertical limits are inducing sprawl and making cities more and more spread out what I find is that
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cities that have more restrictive building height regulations end up having footprints that are not only
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larger but also less compact relative to what their topography and predicted growth would suggest so relaxing these
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constraints would be a way at least to slow down the deterioration in City shape that city growth entails and a
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second policy implication could be related to investments in urban infrastructure one of my findings is
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that the negative consequences of bad city geometry are more pronounced in cities that have a poor road network so
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providing road infrastructure might be a way to compensate consumers for the poor
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shape of the city that they live in well so far in my research I have looked at City level aggregate outcomes and I
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have compared the outlines of cities looking at cross city comparisons what I'd like to do next is take this to a
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more disaggregated level and look at what happens within cities look at the internal structure of cities as a
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follow-up to this project it would be important to understand who bears the costs of longer commutes in cities that
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are not compact what categories of consumers are affected the most perhaps low-income households that don't have
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access to individual means of transportation what consequences if any does City shape have on residential
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patterns and in particular residential segregation by socioeconomic status are some kinds of City shapes more conducive
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to segregation and others more conducive to integration you