Life-cycle Productivity of Industrial Inventors: Education and other determinants

This paper analyzes the life-cycle inventive productivity of Japanese industrial inventors, based on panel data of 1,731 inventors matched with firm data. We focus on two issues: whether inventors with PhD degrees perform better, even taking into account the late start in their business careers, and if those with PhD degrees based only on dissertation (PhDs (DO)), for which a university performs only a certification function, are similarly as productive as the regular PhD holders. Our main findings are the following. Inventors with regular PhD degrees have significantly higher annual productivity than those with other education levels in terms of both patent and forward citation counts, and they can easily compensate for the late start in their business careers. This is the case even after controlling for workplace, research stage, and inventor ability. PhDs (DO) also have high patent productivity (rising more rapidly with experience), although their level is lower than that of regular PhD holders. They work in independent laboratories and in projects involving basic research as frequently as do the regular PhD holders. Furthermore, the exits of PhDs (DO) from inventions are significantly late even when controlling for project type and inventor ability, so that they work longer as inventors.