Table 10. Endogeneity test for the environmental variables (Z variables) of the stochastic tax frontier model.
| Table: Estimation Results | ||||
|---|---|---|---|---|
| Model EX | Model EN | |||
| Dep.var: lnvat | ||||
| Constant | 0.343** | (-0.123) | 0.415** | (-0.134) |
| lnvttl | 0.963*** | (-0.011) | 0.956*** | (-0.012) |
| Dep.var: ln(σ2_u) | ||||
| Constant | 1.712 | (-2.293) | 4.756 | (-3.18) |
| lncpi | -1.032*** | (-0.268) | -1.417*** | (-0.377) |
| lnshad | 0.928* | (-0.393) | 0.714 | (-0.435) |
| lndocimp | 0.732* | (-0.316) | 0.777* | (-0.33) |
| lncostimp | -0.453 | (-0.232) | -0.520* | (-0.22) |
| lntimeimp | -0.637 | (-0.367) | -0.771* | (-0.363) |
| Dep.var: ln(σ2_v) | ||||
| Constant | -5.449*** | (-0.073) | ||
| Dep.var: ln(σ2_w) | ||||
| Constant | -5.461*** | (-0.073) | ||
| eta1 (lncpi) | -0.074 | (-0.055) | ||
| eta2 (lnshad) | -0.018 | (-0.036) | ||
| eta3 (lndocimp) | 0.008 | (-0.022) | ||
| eta Endogeneity Test | X2 = 1.83 | p = 0.609 | ||
| Observations | 416 | 416 | ||
| Log Likelihood | 496.61 | 670.12 | ||
| Mean Tech Efficiency | 0.8462 | 0.8378 | ||
| Median Tech Efficiency | 0.8826 | 0.8734 | ||
Source: Own calculation. Notes: Standard errors are in parentheses. Asterisks indicate significance at the 0.1% (***), 1% (**) and 5% (*) levels.