Table 2: Descriptive statistics and Unit root test with ADF and KPSS______________________________________________________________ Variable Mean Median Maximum Minimum Skewness Kurtosis Jarque-Bera Efp 4.547 4.636 5.839 2.583 -0.619 2.686 3.674 CE 19.193 19.348 22.511 15.681 -0.264 2.672 0.869 CDD 1231.963 1220.500 1480.000 1016.000 0.422 2.873 1.641 HDD 4536.185 4570.500 5029.000 5029.000 3778.000 3778.000 -0.719 0.388 1.801 4.592单位根测试水平δADF与截距截距和趋势截距和趋势结论___ _ lnefp -3.682* -1.798 -5.922* -6.795*混合LNCE -1.517 -1.517 -2.718 -2.718 -4.855* -5.55* -5.474* i(1)LNEFP -1.798 -5.922* -6.795 -7.390* -7.403* i(1)lnhdd -3.961* -6.425* -9.244* -9.145*混合LNGDP -3.230 ** 0.068 -3.531 ** -5.043* I(1) 0.161** 0.403 0.079 Mixed lncooling 0.933* 0.085 0.120 0.059 I (1) lnheating 0.867* 0.046 0.042 0.041 I (1) lnGdp 0.886* 0.226* 0.602** 0.164 Mixed