Unit-Root Tests and the Statistical Pitfalls of Seasonal Adjustment: The Case of U.S. Postwar Real Gross National Product
发现对季节调整后的美国战后季度GNP数据进行单位根检验，强烈支持存在单位根；但使用未调整数据时结论不明确，并解释了季节调整为何可能改变检验结果。
Unit-root tests applied to the postwar seasonally adjusted quarterly gross national product series strongly support the null hypothesis of the presence of a unit root in the data-generating process. Evidence reported here with seasonally unadjusted data is far less conclusive. It is explained why seasonal-adjustment procedures may alter the outcome of conventional tests.