The Cyclical Component of U. S. Economic Activity
使用卡尔曼滤波将1947-1985年美国工业生产和GNP数据分解为趋势和周期成分，发现至少一半的季度波动来自持续长达五年的周期成分，挑战了“波动主要来自趋势”的观点。
Quarterly data on industrial production and deflated gross national product in the United States from 1947 through 1985 are decomposed into independent nonstationary trend and stationary cycle components using Kalman filtering and smoothing techniques. Estimates of the model parameters imply that at least half of the quarterly innovation in U. S. economic activity can be attributed to a stationary cyclical component that persists over periods of time as long as five years. This finding is inconsistent with the hypothesis that most of the apparent variation in U. S. economic activity can be attributed to a nonstationary trend component.