Notes: In the ZA tests, Model A allows for a structural break change in intercept, Model B allows for a structural break in the slope and Model C allows for a change in both the intercept and slope; DU and DT are dummy variables that control the changes in the level and trend, respectively; In the ZA tests, the null hypothesis is that the series has unit root without a structural break against the alternative hypothesis that they are stationary with break; All unit root tests include an intercept and trend; If null hypotheses are rejected in the FKPSS, there is unit root; k* indicates the optimal frequency, while k indicates the optimal number of lags. TB shows the estimated breakdown date. Values in parentheses show the t statistic and values in square brackets represent the test statistics value. δ shows the unit root test statistic values; The critical values for test statistics were taken from Zivot and Andrews (1992). In the ZA test, the table critical values for Model A are −5.34, −4.80, −4.58, for Model B are −4.93, −4.42, −4.1 and for Model C are −5.57, −5.08 and −4.82 for 1%, 5% and 10%, respectively; In the study, Lee and Strazicich (2003, 2004) unit root test allows endogenous one and/or two structural breaks. The results of this test are not included because the dummy variables are not significant. This situation is interpreted as the LM root unit root test could not catch smooth breaks because it captures sharp breaks better; Table critical values of the Fourier KPSS (FKPSS) unit root test are taken from Becker et al. (2006). The table critical values of the Fourier KPSS unit root test are 0.071, 0.054 and 0.047 for k* = 1, and 0.202, 0.133 and 0.103 for k* = 2 and for 1%, 5% and 10%, respectively;

*** and

*imply rejection of the unit root at the 1% and 10% levels, respectively, for ZA; *** and * imply rejection of the no unit root at the 1% and 10% levels, respectively, for FKPSS