Product Innovation by a Durable-Good Monopoly
研究耐用品垄断企业定期推出新产品的速率，发现若无法人为缩短产品寿命或给老客户折扣，创新速率低于社会最优；反之则可实现社会最优。
We consider a durable-good monopolist that periodically introduces new models, each new model representing an improvement upon its predecessor. We show that if the monopolist is able neither to exercise planned obsolescence (i.e., artificially shorten the lift of its products) nor to give discounts to repeat customers, the rate of product introductions is too slow -- in comparison with the social optimum. On the other hand, if the monopolist is able to artificially shorten the durability of its products or to offer price discounts to repeat customers, it can raise its profit and, at the same time, implement the social optimum.