Short and Long Run Externalities

In this paper we build upon previous work on external economies in manufacturing [Caballero and Lyons (1989, 1990)] by providing new evidence helpful for discriminating between different types of externalities. We investigate four-digit level input-output relationships and find that, over shorter horizons, the linkage between an industry and its customers is the most important factor in the transmission of externalities. This suggests that transactions externalities accruing primarily to the seller, and/or activity-driven demand externalities are significant for explaining the short-run behavior of measured total factor productivity. Over longer horizons. on the other hand, it is the activity level of suppliers that is more important. This suggests that external effects are also operating through intermediate goods linkages.