Does Digital Economy Contribute to Regional Carbon Productivity? Evidence of China

Table 3

Unit root test results.

Variable	Testing method	Initial sequence		First difference		Second difference
		Statistic	Prob	Statistic	Prob	Statistic	Prob
	LLC	0.648	0.741	−1.360	0.087	−2.630	0.004
	ADF-Fisher	0.412	0.814	3.681	0.159	6.264	0.044
	PP-Fisher	0.936	0.626	3.806	0.149	5.954	0.051
	LLC	3.533	1.000	−0.907	0.182	−6.240	0.000
	ADF-Fisher	0.005	0.998	2.153	0.341	16.618	0.000
	PP-Fisher	0.003	0.998	2.925	0.232	19.352	0.000
	LLC	1.668	0.952	−1.817	0.035	−4.250	0.000
	ADF-Fisher	0.080	0.961	5.155	0.076	12.191	0.002
	PP-Fisher	0.080	0.961	5.036	0.081	14.204	0.001
	LLC	7.509	1.000	−0.379	0.352	−3.366	0.000
	ADF-Fisher	0.000	1.000	1.327	0.515	9.863	0.007
	PP-Fisher	0.000	1.000	1.065	0.587	10.556	0.005
	LLC	0.318	0.625	−2.047	0.020	−2.929	0.002
	ADF-Fisher	0.574	0.751	5.908	0.052	8.553	0.014
	PP-Fisher	0.604	0.739	5.890	0.053	8.602	0.014
	LLC	0.318	0.625	−2.047	0.020	−2.929	0.002
	ADF-Fisher	0.574	0.751	5.908	0.052	8.553	0.014
	PP-Fisher	0.604	0.739	5.890	0.053	8.602	0.014
	LLC	2.041	0.979	−3.034	0.021	−4.834	0.000
	ADF-Fisher	0.065	0.968	9.219	0.060	13.618	0.001
	PP-Fisher	0.004	0.998	9.219	0.052	17.632	0.000

Note., , and indicate the significance at the level of 0.01, 0.05, and 0.1, respectively.