R&D and patents: is it a two way street?

This paper provides empirical evidence on the link between firms' R&D expenditure and patent registrations by applying the Granger causality test. We use a panel of Spanish manufacturing firms for the period 1990-2013. We first, examine the R&D-patents relationship in the manufacturing firms as a whole and subsequently, manufacturing was broken down into three groups of firms according to the technological level of the industries to which the firms belonged: high and medium-high (HMHT), low medium (LMT) and low (LT) technology firms. For the entire panel, our results provide support for a bidirectional relationship between R&D and patents, supporting both the traditional view and the reverse causality approach (patents cause R&D). When the sample is split into the three technology levels, we also find strong support for a bidirectional relationship in HMHT firms and weak support in LT ones. We found no evidence of this bidirectional link in LMT firms.