Collaborative Research: Obsolescence of Durable Goods and Aggregate Fluctuations

在技术创新率较高的市场中，过时是耐用品折旧的主要原因。由于许多技术创新都被纳入到新的耐用品中，耐用品的过时建模对于我们理解宏观经济是至关重要的。考虑耐久性的主要方式是指数物理折旧。陈旧与实物折旧在两个重要方面不同。首先，淘汰不是一个连续的过程。新产品的开发成本很高，这就是为什么新产品只能定期推出的原因。例如，每年都会出现新的车型，平均每三年就会出现新一代的英特尔处理器。因此，新车型的周期性到来使过时的车型变得离散。其次，随着过时，从好的服务流是由它的技术时代定义的。计算机因为不能运行最新的软件而被淘汰。当最新车型上市时，新车库存会大幅打折，这表明过时在汽车中也很重要。由于耐用品即使从未使用过也会老化，延迟购买新型号的消费者将享受到较低的服务流。因此，过时让消费者有动力将他们的更换决定与新车型的推出协调起来。这种关于陈旧的思维方式以前没有得到充分的探索，但它可能会对宏观经济波动的模式产生深远的影响。这个项目研究了一类具有耐用品被淘汰的动态经济。它看起来是一个具有竞争性的耐用品生产的一般均衡模型，以及具有战略生产者的耐用商品市场模型。

Obsolescence is the major reason for depreciation of durables in markets with high rates of technological innovation. Since much of the technological innovation is incorporated in new durables, modeling obsolescence of durable goods is vital for our understanding of the macroeconomy. The dominant way of thinking about durability is in terms of exponential physical depreciation. Obsolescence is different from physical depreciation in two important respects. First, obsolescence is not a continuous process. Development of new products is costly, which is why new goods are introduced only periodically. For example, new car models appear every year, and new generations of Intel processors appear on average, every three years. Thus periodic arrival of new models makes obsolescence discrete. Second, with obsolescence, the service flow from the good is defined by its technological age. Computers become obsolete because they cannot run the latest software. New car inventory is heavily discounted when the latest models arrive, suggesting that obsolescence is important in cars as well. Since durables age even if never used, consumers who purchase a new model with a delay will enjoy a lower service flow. Thus obsolescence gives consumers an incentive to coordinate their replacement decisions with new model introductions. This way of thinking about obsolescence has not been fully explored before, yet it may have profound effects on the patterns of macroeconomic fluctuations. This project studies a class of dynamic economies with durable goods subject to obsolescence. It looks a general equilibrium models with competitive production of durable goods as well as models of durable good markets with strategic producers.