Omay, TolgaGupta, RanganBonaccolto, Giovanni2017-11-302017Tolga Omay, Rangan Gupta & Giovanni Bonaccolto (2017) The US real GNP is trend-stationary after all, Applied Economics Letters, 24:8, 510-514, DOI: 10.1080/13504851.2016.1205719.1350-4851 (print)1466-4291 (online)10.1080/13504851.2016.1205719http://hdl.handle.net/2263/63405This article applies the Fractional Frequency Flexible Fourier Form (FFFFF) Dickey–Fuller (DF)-type unit root test on the natural logarithm of US real GNP over the quarterly period of 1875:1–2015:2, to determine whether the same is trend- or difference-stationary. While standard and Integer Frequency Flexible Fourier Form DF-type test fails to reject the null of unit root, the relatively more powerful FFFFF DF-type test provides strong evidence of the real GNP as being trend-stationary, i.e. US output returns to a deterministic log-nonlinear trend in the long run.en© 2016 Informa UK Limited, trading as Taylor & Francis Group. This is an electronic version of an article published in Applied Economics Letters, vol. 24, no. 8, pp. 510-514, 2017. doi : 10.1080/13504851.2016.1205719. Applied Economics Letters is available online at : http://www.tandfonline.com/loi/rael20 [18 months embargo]Fractional frequency flexible Fourier form (FFFFF)Structural breakUnit rootUS real GNPGross national product (GNP)Postprint Article