Does Gnp Have a Unit Root? a Reevaluation

Stock and Watson (1986) Tests the Hypothesis That Real Per Capita Gnp Has a Unit Root by Using a Test Statistic Due to Phillips (1985) Which Incorporates a Nonparametric Correction for the Serial Correlation Induced by System and Error Dynamics. the Version of This Test That Is Used by Stock and Watson Does Not Accomodate the Presence of a Drift and to Compensate They Detrend the Series by Extracting a 1.5% Annual Trend Growth. We Use a Version of This Class of Nonparametric Tests, Developed by Phillips and Perron (1986), Which Allows for an Estimated Drift and Reassess the Stock and Watson Findings.