The Crowding-Out Effects of Long Duration of Patents
构建世代交叠模型，证明专利期限过长会挤占年轻人对新产品开发的投资，从而降低创新率，对依赖专利激励创新的传统观点提出挑战。
In this article we demonstrate how a long duration of patents affects investment in new product development. We construct an overlapping-generations model of saving, investment, and product innovation and show that a long duration of patents results in a high aggregate value of monopoly firms that compete for the younger generation's savings with investment in new product development. We analyze the effects of long duration of patents and their implications for individuals' welfare under different patent regimes. * It is widely accepted that the patent system is useful for encouraging new product development despite the market distortion it creates by granting temporary monopoly rights to new firms. Thus, the patent system is essential to growing economies. It is commonly believed that a long duration of patents (long duration of monopolies) increases the incentives for firms to engage in product development and therefore increases the rate of product development in the economy. The purpose of this article is to show that when one takes into account the effects of an increase in the number of monopoly firms on savings, this is not necessarily the case. We develop a multiproduct, general-equilibrium, overlapping-generations model of product innovation, in which the savings of the young can be used to purchase monopoly firms from older generations and/or can be allocated to the process of innovation, which involves the construction of new firms (new products). A long duration of patents is associated with monopoly firms that maintain their monopoly rights for many generations. Thus, an increase in the patent life increases the number of existing monopoly firms sold by the old to the young each period, and therefore it increases the fraction of the young's savings allocated to purchasing existing monopoly firms from the old and decreases the fraction of savings allocated to the construction of new firms (the development of new products) .' We define the concept of the crowding-out effect as a situation where part of