This paper reviews the recent empirical literature on international
knowledge spillovers. I start by summarizing the theoretical models that have highlighted
the potential importance of these spillovers. Then, drawing upon the older micro
productivity research tradition, I lay out a simple conceptual framework (though not a
formal theoretical framework) for thinking about the various kinds of knowledge transfers
that may exist, how they might be mediated, and the means by which their effects might
be traced empirically. I then review some influential empirical papers, demonstrating
that empirical work to date may very well not have identified the effects the authors set
out to measure. Finally, I describe some promising new approaches which may allow
researchers in this field to identify more precisely, both conceptually and empirically,
certain kinds of international knowledge spillovers.