This study presents a model in which firms invest in research and development (R&D) to generate innovations that increase their underlying profitability and invest in physical capital to produce output. Estimating the model using a method of moments approach reveals that R&D expenditures...

Most work on social interactions studies a single, composite effect of interactions within a group. Yet in the case of sexual initiation, there are two distinct social mechanisms-peer-group norms and partner availability-with separate effects and different potential interventions. Here I develop...