It should be noted, however, that the precise
magnitude of these returns cannot be
measured without the use of simplifying
assumptions in the analysis. A survey article by
Nadiri (1993) examined 63 studies in this area
published by prominent economists, mostly in
reference to the United States, but also in
reference to Japan, Canada, France, and
Germany. Looking at the results of these
studies, he concluded that R&D activity
renders, on average, a 20 to 30 percent
annual return on private (industrial)
investments