Table 3 The results of the Ng-Perron unit root test

EG_R (1)*

− 1.194

− 0.808

0.860

7.054

− 4.016

− 1.232

0.481

8.629

− 3.031

− 0.247

0.518

9.614

EU_A (1)*

− 0.851

− 0.251

0.711

5.361

− 0.908

− 0.946

0.543

7.175

− 0.076

− 0.038

0.580

8.160

EP (1)*

− 1.078

− 0.014

0.522

5.698

− 16.122

− 1.665

0.216

6.739

− 15.137

− 0.680

0.254

7.724

HC_IN (1)*

− 3.945

− 0.295

0.983

8.293

− 2.345

− 1.138

0.671

9.139

− 1.360

− 0.153

0.708

10.124

ΔEG_R (0)*

− 9.121

− 2.406

0.173

3.793

− 23.942

− 2.542

0.179

4.655

− 22.957

− 1.557

0.217

5.640

ΔEU_A (0)*

− 13.911

− 1.566

0.209

3.279

− 37.600

− 3.386

0.151

3.456

− 36.615

− 2.401

0.188

4.441

ΔEP (0)*

− 13.689

− 1.713

0.221

2.692

− 19.023

− 2.177

0.195

5.539

− 18.038

− 1.192

0.233

6.524

ΔHC_IN (0)*

− 10.156

− 0.999

0.153

1.862

− 27.775

− 6.334

0.083

2.449

− 26.790

− 5.349

0.121

3.434

Ng-Perron critical value 5%

− 7.115

− 0.995

0.270

4.155

− 16.315

− 1.925

0.205

6.465

− 15.330

− 0.940

0.243

7.450