Vertical Industry Linkages: Sources Of Productivity Gains And Cumulative Causation

In this paper we analyse vertical industry linkages, and the extent to which these work as channels for externalities. First, we test for activity-based externalities stemming from output growth and output level in vertically linked industries. Second, we aim at revealing the importance of a large home market for upstream industries. Eventually, by comparing results on localized inter-industry externalities and on the impact of local sales, we try to identify to what extent the geographical agglomeration of an industry is self-reinforcing. A number of Norwegian maritime transport and services sectors are analysed. The results are promising in the sense that the model distinguishes empirically between different sources of externalities, and unveils which vertical linkages that give rise to endogenous agglomeration.