Most of our productive knowledge was handed down to us by previous generations. The transfer of knowledge from the old to the young is therefore a cornerstone of productivity growth. We study this process in a model in which the old sell knowledge to the young - - old workers train the young,...

We model research as a signal on an unknown parameter of a technology. We distinguish applied from basic research and show that firms in the same industry can optimally choose different research portfolios, and that basic research can seem to have a higher rate of return than applied research,...

In a Bayesian model of learning, the more an agent uses a technology, the better he learns its parameters. This expertise is a form of human capital. Switching to a new technology temporarily reduces expertise: the bigger the leap, the bigger the loss. This may prevent the agent from climbing...

People at the top of an occupational ladder earn more partly because they have spent time on lower rungs, where they have learned something. But what precisely do they learn? There are two contrasting views: First, the Bandit model assumes that people are different, that experience reveals their...

This paper explores a one-agent Bayesian model of learning by doing and technological choice. To produce output, the agent can choose among various technologies. The beneficial effects of learning by doing are bounded on each technology, and so long-run growth in output can take place only if...