We study the effect of the fragmentation of intellectual property rights on optimal patent design. The major finding is that when several complementary innovative components must be assembled to operate a new technology, the patentability requirements should be stronger than in the case of...

I model environmental overcompliance as a signalling device. In the model, a benevolent government may or may not tighten environmental standards. Production costs under the stricter environmental regulation are private information to the firms, and tightening environmental policy is socially...

We study a quality-ladder model of endogenous growth that produces stochastic leadership cycles. Over a cycle, industry leaders can innovate several successive times in the same industry, gradually increasing the magnitude of their technological lead before being replaced by a new entrant....