Public and private investment in R&D: complementary effects and interaction with productivity growth

The purpose of this paper is to analyze the relationship between public and private research expenditures since can provide main information to policy makers to improve the economic performance of country. The main results are: Public R&D expenditure is a complement for private R&D one but the latter has to be higher than the former to be a determinant for productivity growth of countries. These results can be affected by several factors concerning the structure of National System of Innovation and Triple helix mechanism. In addition this research shows that the composition of public and private magnitude of national investment in research depends on the level of country development.