Table 10.

Robustness analysis of subsample regression.

Dependent	$\theta$	$\theta$	$\theta$	$\theta$	$\theta$	$\theta$
Method	Panel Tobit	Panel Tobit	Panel Tobit	Panel Tobit	Panel Tobit	Panel Tobit
Sample	Year ≠ 2014	Year ≠ 2016	Year ≠ 2019	Year ≠ 2014	Year ≠ 2016	Year ≠ 2019
$x_1$	−0.009*** (−4.21)	−0.011*** (−4.91)	−0.011*** (−5.65)
$x_2$				−0.064*** (−12.60)	−0.073*** (−13.23)	−0.072*** (−14.59)
Control variables	Yes	Yes	Yes	Yes	Yes	Yes
${\tau }_i$	Yes	Yes	Yes	Yes	Yes	Yes
N	405	405	405	405	405	405

Notes: The parentheses in the table are t-statistics or z-statistics, and ***, **, and * indicate passing significance tests at the 1%, 5%, and 10% levels, respectively.