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CEP discussion paper
Is Distance Dying at Last? Falling Home Bias in Fixed Effects Models of Patent Citations
Rachel Griffith, Sokbae Lee and John Van Reenen August 2007
Paper No' CEPDP0818:
Full Paper (pdf)

JEL Classification: O32; O33; F23

Tags: fixed effects; home bias; patent citations; knowledge spillovers

We examine the “home bias” of international knowledge spillovers as measured by the speed of patent citations (i.e. knowledge spreads slowly over international boundaries). We present the first compelling econometric evidence that the geographical localization of knowledge spillovers has fallen over time, as we would expect from the dramatic fall in communication and travel costs. Our proposed estimator controls for correlated fixed effects and censoring in duration models and we apply it to data on over two million citations between 1975 and 1999. Home bias declines substantially when we control for fixed effects: there is practically no home bias for the more “modern” sectors such as pharmaceuticals and information/communication technologies.