We simultaneously assess the contributions to productivity of three sources of research and development spillovers: geographic, technology and product-market proximity. To do this, we construct a new measure of geographic proximity that is based on the distribution of a firm's inventor locations...

Intelligently allocating research effort and funds requires deciding whether to build on recent advances or on more established knowledge. When recent advances create superior opportunities for invention, their adoption as research inputs in the invention process promotes technological progress....

We develop a model of induced innovation where research effort is a function of the death rate, and thus the potential to reduce deaths in the population. We also consider potential social consequences that arise from this form of induced innovation based on differences in disease prevalence...

We investigate rewards to R&D in a model where substitute ideas for innovation arrive to random recipients at random times. By foregoing investment in a current idea, society as a whole preserves an option to invest in a better idea for the same market niche, but with delay. Because successive...