In active investment climates where firms sequentially improve each other's products, a patent can terminate either because it expires or because a non-infringing innovation displaces its product in the market. We define the length of time until one of these happens as the effective patent life,...

In active investment climates where firms sequentially improve each other's products, a patent can terminate either because it expires or because a noninfringing innovation displaces it in the market. The patent breadth and patent life together determine which of these occurs first. We...

Incorporating space in economic models has two important consequences. First, the hypothesis of perfect competition becomes untenable, and second, the distinction between private and public goods becomes blurred. We review arguments that lead to these conclusions and summarize recent work...