We present a model of industry evolution where the dynamics are driven by a process of endogenous innovations, followed by subsequent embodiments in physical capital. Traditionally, the only distinction between R&D and physical investment was one of labeling: the first process accumulates an...

This paper studies optimal investment policies when the production function depends on capital of various vintages. In such an environment it is natural to ask whether the firm will invest in old-vintage capital at all. In this paper I derive such a condition. Predictably, investment in old...

This paper extends Lucas (1978) to a production economy with two capital goods. It is an RBC model in which each unit of investment requires a new idea, an "option". When options are scarce, new capital is harder to put in place and the value of old capital rises. Thus the stock market and...

We present a model of industry evolution where the dynamics are driven by a process of endogenous innovations, followed by subsequent embodiments in physical capital. Traditionally, the only distinction between R&D and physical investment was one of labeling: the first process accumulates an...