Collaborative Research: Obsolescence of Durable Goods and Aggregate Fluctuations

在技术革新率高的市场上，过时是耐用品贬值的主要原因。由于许多技术创新都与新的耐用品相结合，因此对耐用品过时的建模对于我们理解宏观经济至关重要。考虑耐久性的主要方式是根据指数物理折旧。过时与实物折旧在两个重要方面有所不同。首先，过时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是定期推出的原因。例如，新车型每年都会出现，新一代英特尔处理器平均每三年出现一次。因此，新模型的周期性到来使得过时变得离散。其次，随着过时，来自商品的服务流由其技术时代定义。电脑过时是因为它们不能运行最新的软件。当最新车型到货时，新车库存会大幅打折，这表明汽车的过时也很重要。由于耐用品即使从未使用过也会老化，因此消费者购买延迟购买的新型号将享受较低的服务流量。因此，过时给了消费者一种激励，促使他们在新车型推出时做出更换决定。这种关于过时的思考方式以前尚未得到充分探讨，但它可能对宏观经济波动的模式产生深远的影响。本项目研究一类具有易过时耐用品的动态经济体。研究了具有耐用品竞争性生产的一般均衡模型以及具有战略生产者的耐用品市场模型。

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.