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On The Ellison–Glaeser Geographic Concentration Index, Edward J. Feser

Edward J Feser

I use confidential employment data to investigate the empirical properties of a recent industry geographic concentration index (and related index of industry co-agglomeration) proposed by Ellison and Glaeser (1997). The results show that Ellison and Glaeser’s theoretical finding that their concentration measures are robust to differences in the level of spatial aggregation in the underlying employment data does not generally hold in practice. This implies that sensitivity testing for alternative spatial units should accompany any analysis with the concentration measures.