Product Cycles in U.S. Imports Data
构建了美国制造业新产品进口数据，发现北方国家的新产品出口增长快于南方，但十多年后南方追赶并逆转，且产品周期随时间缩短、与技术相关。
In this paper, I construct product-level U.S.-manufacturing-imports data for new products. I show that consistent with product cycles, the North's new-products exports to the United States, relative to its old-products exports, grow faster than the South's for over a decade; then the South catches up with the North, and this pattern is reversed. This finding holds up in parametric, nonparametric, and semiparametric estimations, and only when new products are properly identified and old products within the same industries are used as controls. There is also evidence that product cycles become shorter over time and they are technology related.