Crossover inventions and knowledge diffusion of general purpose technologies?

"Scholars have long noted the significant impact of general purpose technologies (GPTs) on the economy. However, limited attention has been paid to exploring how they are employed to generate inventions in downstream sectors (crossover inventions), and what factors may facilitate such diffusion. We study these issues by examining the introduction of one of the widely regarded GPTs -- electrical technology -- in the late 19th century U.S. We find that knowledge spillovers between industries (inter-industry spillovers and learning-by-using) had little influence on the geography of crossover inventions as well as the speed and productivity of inventors at making them. Instead, appropriate human capital and an environment promoting inventions in general played a more important role"--National Bureau of Economic Research web site.