Market Potential, panel data, and aggregate fluctuations: All that glitters is not gold

The New Economic Geography (NEG) provides a historical explanation for the spatial agglomeration of economic activity. One of its predictions, the ‘wage equation’, relates regional income to market accessibility. Although the NEG is a long-term theory, empirical literature has tested it using panel data methods, which capture short-term relation-ships between temporal changes in variables. For a sample of European regions, I show that panel data estimations of the wage equation identify only potential spillover effects of the European business cycle on the synchronic evolution of regional per capita income. That is, the panel data results are not due to the mechanisms proposed by the NEG. The paper concludes with a cautionary note about misinterpretation of panel data estimations.