Jovanovic, B., & Nyarko, Y. (1995). A Bayesian Learning Model Fitted to a Variety of Empirical Learning Curves. Brookings Papers on Economic Activity. Microeconomics, (1), 247-305.
Where does technological progress come from and what determines its rate of advance? In answering these questions, it is useful to decompose technological progress into the invention of new techniques and products and the improvement of existing ones.