Machines are more expensive in poor countries, and the relation is pronounced. It is hard for a Solow (1956) type of model to explain the relation between machine prices and GDP given that in most countries equipment investment is under 10% of GDP. A stronger relation emerges in a Solow (1959)...

This paper deals with processes that require several complementary inputs subject to improvements in quality. If after a quality upgrade one of these inputs requires a period of learning before it can be used effectively, then in general it will pay to purchase the inputs at different dates --...

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,...

Product-recall data and information on stock-price reactions to recalls are used to estimate the value of reputation in a model in which product quality is not contractible. A recall is the result of a product defect that signals low effort. The recall triggers a reduction in the firm's product...

Cyclical patterns in earnings can arise when contracts between firms and their workers are incomplete, and when workers cannot borrow or lend so as to smooth their consumption. Effort cycles generate occasional large changes in earnings. These large changes are transitory, consistent with recent...

We study private equity in a dynamic general equilibrium model and ask two questions: (i) Why does the investment of venture funds respond more strongly to the business cycle than that of buyout funds? (ii) Why are venture funds returns higher than those of buyout? On (i), venture brings in new...

We study the effects of parameter uncertainty prompted by structural breaks. In our model, agents respond differently to uncertainty prompted by regime shifts in shock processes than they react to comparable perceived increases in shock volatility. The magnitude of the response to an increase in...

This paper documents several facts on the real effects of economic uncertainty. First, higher uncertainty is associated with a more dispersed distribution of output growth. Second, the relation is highly asymmetric: A rise in uncertainty is associated with a sharp decline in the lower tail of...

We study the innovation and diffusion of technology at the industry level. We derive the full dynamic paths of an industry's evolution, from birth to its maturity, and we characterize the impact of diffusion on the incentive to innovate. The model implies that protection of innovators should be...

The prospect of capital obsolescence inhibits investment. Investors thus become more optimistic when the obsolescence of their capital slows down. We propose a model with no fixed costs of investment, and random technological progress that induces obsolescence of capital in place. Spikes occur...