Table 2

Zero-inflated Poisson regression with number of sick days as the dependent variable

	Model 1	Model 2	Model 3	Model 4
Count component
Age	−0.016	−0.017	−0.049	−0.031
Age squared	0.0002	0.0002	0.0007	0.0005
Previous deliveries			0.374	0.330
Previous deliveries×age			−0.008	−0.007
II Lower professionals				0.056
IIIa Higher routine				0.185
IIIb Lower routine				0.240
V Technicians				0.069
VI Skilled				0.212
VIIa Semiskilled and unskilled				0.285
VIIb Agricultural				0.200
Missing				0.107
Constant	4.448	3.350	3.749	3.231
Excess zero component
Constant	−1.341	−1.341	−1.341	−1.341
Observations	216 541	216 541	216 541	216 541
Cragg and Uhler's	0.023	0.179	0.290	0.462

The coefficients in the count component are adjusted for Working hours, Leave, Year and Marital status in models 2–4. The coefficients of the excess zero component are adjusted for Working hours and Leave in all four models.