摘要：It is shown that spillovers can enhance private returns to innovation if they
feed back into the dynamic research of the original inventor (Internalized
spillovers), but will always reduce private returns, if the original inventor
does not benefit from the advancements other inventors build into the “spilled”
knowledge (Externalized spillovers). I empirically identify unique patterns of
knowledge flows (based on patent citations), which provide information about
whether “spilled” knowledge is reabsorbed by its inventor. A simple model of
sequential innovation with dynamic spillovers is developed, which predicts that
market value and R&D expenditures should rise with Internalized spillovers
and fall with Externalized spillovers. These predications are confirmed using
panel data on U.S. firms between 1981 and 2001. To the extent that firms
internalize some of the spillovers they create, the classical underinvestment
problem in R&D will be mitigated and the central role of spillovers in
promoting economic growth will be enhanced.
