Key points are not available for this paper at this time.
This finding may reflect both the fact that, relatively speaking, manufacturing industries do not "import" much R&D (though they "export" a lot to non-manufacturing industries) and that at the more disaggregated levels used by us Scherer's estimates are based on smaller samples and may be subject to more significant errors in variables problems.On the first point, see Scherer (1982b, p. 233).
Griliches et al. (1984) studied this question.