Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
Most of the empirical studies in the literature on intra-industry trade are conducted at the country level. Countries, however, differ in terms of granularity and internal heterogeneity. In the present study we empirically identify the determinants of the overall IIT as well as its horizontal and vertical components in the trade of Spanish and Polish NUTS-2 regions with all existing trade partners over the period 2005–2014. In order to obtain unbiased results, we utilize a semi-mixed effect model, estimated with the PPML method. We estimate the models jointly for all Spanish and Polish regions and then disjointly in a comparative manner – in order to identify incongruities of reaction to the various factors investigated. These include both traditional factors and a number of unorthodox factors such as regional path dependence, quality of regional institutions, the core or peripheral status of the reporting region.