We build a model of firm-level innovation, productivity growth and reallocation featuring endogenous entry and exit. A new and central economic force is the selection between high- and low-type firms, which differ in terms of their innovative capacity. We estimate the parameters of the model...

We develop a microeconomic model of endogenous growth where clean and dirty technologies compete in production and innovation. in the sense that research can be directed to either clean or dirty technologies. If dirty technologies are more advanced to start with, the potential transition to...

We build a tractable growth model where multi-product incumbents invest in internal innovations to improve their existing products, while new entrants and incumbents invest in external innovations to acquire new product lines. External and internal innovations generate heterogeneous innovation...