英语翻译Column 1 in Table 1 shows the social rate of return to i

英语翻译Column 1 in Table 1 shows the social rate of return to industry from R&D conducted byfirms within the same industry.These estimates range from 17% to 34%.The secondcolumn shows the social return attributable to R&D conducted in one industry but used inanother (for example,R&D carried out in an upstream industry).Estimates of the socialrate of return on this R&D are significantly higher.Adding the two together implies asocial rate of return of around 100%.These estimates are largely based on data for themanufacturing sector.Empirical results on the social rate of return to R&D are integrated into a macroeconomicmodel of endogenous innovation and growth by Jones and Williams (1998).They showthat the estimates of the social rate of return in the R&D literature (i.e.the studies shownin Table 1) actually provide a lower bound to the true social rate of return,once we takeinto account the dynamic general equilibrium effects emphasised in the endogenousgrowth literature.Another way in which these models will underestimate the social rate of return to R&D isthat they assume that imitation is costless.However,knowledge is ‘tacit’ in nature:ittakes time and effort to explain new ideas to others and to codify inventions in manualsand textbooks.This means that imitation itself can be costly.6 Recent work hasemphasised the role that R&D plays,not only in leading to new innovations but also inenhancing firms’ ability to imitate.R&D not only stimulates innovation but also plays animportant role in the adoption of existing technologies.Empirical evidence lends supportto these ideas.Griffith,Redding and Van Reenen (2000) present an empirical framework in which therate of return to R&D is composed of an effect on productivity through innovation and aneffect through increased potential for imitation.This second component will beparticularly important for firms,industries and countries far behind the technologicalfrontier.Innovation and technology transfer provide two potential sources of productivitygrowth for countries behind the technological frontier.A country’s distance from thetechnological frontier is used as a direct measure of the potential for technology transfer,where the frontier is defined for each industry as the country with the highest level oftotal factor productivity (TFP).The further a country lies behind the technologicalfrontier,the greater the potential for R&D to increase TFP growth through technologytransfer from more advanced countries.7Griffith et al.(2000) provide econometric evidence that R&D expenditure plays a role inassimilating the research discoveries of others as well as its conventional role as a sourceof innovation.