Agglomerative Forces and Cluster Shapes

William R. Kerr; Scott Duke Kominers

Article | Review of Economics and Statistics | October 2015

Agglomerative Forces and Cluster Shapes

by William R. Kerr and Scott Duke Kominers

Abstract

We model spatial clusters of similar firms. Our model highlights how agglomerative forces lead to localized, individual connections among firms, while interaction costs generate a defined distance over which attraction forces operate. Overlapping firm interactions yield agglomeration clusters that are much larger than the underlying agglomerative forces themselves. Empirically, we demonstrate that our model's assumptions are present in the structure of technology and labor flows within Silicon Valley. Our model further identifies how the lengths over which agglomerative forces operate influence the shapes and sizes of industrial clusters; we confirm these predictions using variations across patent technology clusters.

Keywords: agglomeration; clusters; networks; industrial organization; Silicon Valley; entrepreneurship; Technology Flows; patents; Networks; Technology; Industry Clusters; Entrepreneurship; California;

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Kerr, William R., and Scott Duke Kominers. "Agglomerative Forces and Cluster Shapes." Review of Economics and Statistics 97, no. 4 (October 2015): 877–899.

This paper develops a class of equilibrium-independent predictions of competitive equilibrium with indivisibilities. Specifically, we prove an analogue of the “Lone Wolf Theorem” of classical matching theory, showing that when utility is perfectly transferable, any agent who does not participate in trade in one competitive equilibrium must receive her autarky payoff in every competitive equilibrium. Our results extend to approximate equilibria and to settings in which utility is only approximately transferable.

Hatfield and Kominers (2012) introduced a model of matching in networks with bilateral contracts and showed that stable outcomes exist in supply chains when firms' preferences over contracts are fully substitutable. Hatfield and Kominers (2012) also asserted that in their setting, full substitutability is equivalent to the assumption that all indirect utility representations of each firm's preferences are quasisubmodular; we show here that this claimed equivalence result does not hold in general. We show instead that full substitutability is equivalent to weak quasisubmodularity of all indirect utility representations.

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Agglomerative Forces and Cluster Shapes

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