Study on the Operation Efficiency of Toll Roads in China from the Perspective of Scale Economy
Table 5
Robustness test results.
(I)
(II)
(III)
(IV)
Pooled OLS
Panel GMM
Exp_per_land
7.526
1.360
7.287
3.135
(4.43)
(2.00)
(3.07)
(2.67)
Urban
−0.0156
−0.00147
−0.00972
−0.00257
(−3.10)
(−0.98)
(−2.12)
(−1.22)
Unemploy
−0.164
−0.0411
−0.152
−0.0926
(−2.64)
(−2.34)
(−3.20)
(−12.52)
Eply
0.152
0.0334
0.122
0.0519
(3.00)
(1.67)
(2.85)
(2.53)
Toll_Station
−1.095
0.734
−1.525
1.121
(−2.60)
(5.03)
(−2.46)
(7.51)
Ltc
0.166
0.116
0.179
0.122
(5.12)
(6.78)
(4.36)
(15.09)
Ave_Salary
0.197
−0.0385
0.582
0.317
(0.77)
(−0.25)
(1.81)
(2.71)
_cons
0.573
0.286
−0.242
−0.0358
(0.82)
(1.10)
(−0.30)
(−0.19)
Hansen
—
—
1
1
AR
—
—
0.107
0.101
N
174
174
145
145
Note.Statistical significance at the 10% level; statistical significance at the 5% level; statistical significance at the 1% level. The t-statistics calculated with the standard error of heteroscedasticity are reported in brackets.
