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Social Interaction and Urban Sprawl




Various authors, most notably Putnam (2000), have argued that low-density living reduces social capital and thus social interaction, and this argument has been used to buttress criticisms of urban sprawl. If low densities in fact reduce social interaction, then an externality arises, validating Putnam’s critique. In choosing their own lot sizes, consumers would fail to consider the loss of interaction benefits for their neighbors when lot size is increased. Lot sizes would then be inefficiently large, and cities excessively spread out. The paper tests the premise of this argument (the existence of a positive link between interaction and density) using data from the Social Capital Benchmark Survey. In the empirical work, social interaction measures for individual survey respondents are regressed on census-tract density and a host of household characteristics, using an instrumental-variable approach to control for the potential endogeneity of density.

5. Conclusion

Various authors, most notably Putnam (2000), have argued that low-density living reduces social interaction, and this argument has been used to buttress criticisms of urban sprawl. But urban expansion must involve market failures if it is to be inefficient, and this paper shows that such a distortion indeed arises if low density depresses social interaction. Then, in appraising the gains from greater individual consumption of living space, consumers fail to consider reduced interaction benefits for their neighbors, which arise through lower neighborhood density. Space consumption is then too high, and cities are excessively spread out.

The key element in this argument is a positive link between social interaction and neighborhood density, and the paper tests empirically for such a link. The results are unfavorable:

whether the focus is friendship-oriented social interaction or measures of group involvement, the empirical results show a negative, rather than positive, effect of density on interaction. The paper’s findings therefore imply that social-interaction effects cannot be credibly included in the panoply of criticisms directed toward urban sprawl. In fact, the results suggest an opposite line of argument. With a negative effect of density on interaction, individual space consumption would tend to be too low rather than too high, tending to make cities inefficiently compact, as explained in section 2. Thus, the empirical results suggest that social-interaction effects may counteract, rather than exacerbate, the well-recognized forces (such as un priced traffic congestion) that cause cities to over expand.

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Richard Carson’s Comments:

A major nationwide study done by these professors from Dublin City University and the University of California (Social Interaction and Urban Sprawl, CESifo Working Paper Series No. 1843, November 2006) – of some 15,000 individuals in average urbanized-area and MSA (metropolitan statistical areas) populations – finds that:

“The frequency of interaction with neighbors is lower in high-density census tracts.”

“That residents living in dense census tracts have fewer confidants.”

“High tract density reduces the number of friends.”

“Interactive individuals sacrifice something by locating in dense tracts.”

“Membership in hobby-oriented club is less likely [in low-density tracts].”

“Group involvement tends to be weaker [in low-density tracts].”

The statistical revelation behind all of these findings is that for every 10% increase in density, there is a 10% decrease in socialization. That’s a simple, one-to-one inverse relationship that everyone can understand.

Of course this scientifically researched revelation begs the question, “Why is this so?” The authors of the study suggest that “crowding associated with a dense environment might spur a need for privacy, causing people to draw inward. Such behavior could reflect the old saying: ‘good fences make good neighbors.’” The authors’ conclusion is that “density has been shown to exert a negative influence on social interaction, undermining an important line of attack used by critics of urban sprawl.” This may be an inconvenient truth for the New Urbanist movement, but this negative view of density is hardly new. In fact, it is one supported by such scientific legends as the late Carl Sagan and Ian McHarg

Thanks to the Antiplanner for bringing this paper to our attention