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 its product in the market. We define the length of time until one of these happens as the effective patent life,...

Marshallian districts are locales that accommodate a large number of small firms producing similar goods to be exported and benefit from the accumulation of know-how associated with workers residing there. We study the making of such districts by assuming that the cost function of a firm is a...