Table 2.

Model estimation results.

	Model 1	Model 2	Model 3	Model 4(IV)
LI (labour intensity)	0.0054* (0.0645)	0.0263* (0.0232)	0.3723** (0.0406)	0.4655*** (0.0308)
Age	-	0.5766** (0.1433)	0.4725* (0.4407)	0.6724*** (0.3423)
Academic	-	-	0.2724* (0.1425)	0.2215** (0.3087)
Gender	-	-	-	0.1212 (0.5013)
Instrumental variable	-	-	-	0.3016** (0.4371)
R 2	0.432	0.397	0.365	0.412
Adjusted R-square	0.7378	0.6162	0.5164	0.7188
F	23.56***	25.77***	28.32***	22.66***

***P ≤ 0.001, **P ≤ 0.01, *P ≤ 0.05; Robust standard error in brackets.

Source: authors' own.