Tracing mobile inventors - The causality between inventor mobility and inventor productivity

This paper analyses the causality between inventor productivity and inventor mobility. The results show that the level of education has no influence on inventor productivity. Making use of external sources of knowledge, on the contrary, has a significant effect on productivity. Finally, firm size has a positive impact on productivity. Firm size also influences inventor mobility, although negatively. Whereas existing research- implicitly assumes causality to point in one direction, this study ex ante allows for a simultaneous relationship. To deal with the expected endogeneity problem, instrumental variables techniques (IVREG and IVPROBIT) will be employed. Results show that mobile inventors are more productive than non-movers. Whereas a move increases productivity, an increase in productivity decreases the probability to observe a move. (c) 2007 Elsevier B.V. All rights reserved.