The Treasury

Global Navigation

Personal tools

4.1  Estimation results (continued)

Table 2 – Joint Wage and Selection Models, Single Men and Women
  Wage equation Selection equation
  Single men Single women Single men Single women
  Coef. z-value Coef. z-value Coef. z-value Coef. z-value
  Coef. z-value Coef. z-value Coef. z-value Coef. z-value
  Single men Single women Single men Single women
  Wage equation Selection equation
age/10 0.6892 17.65 0.5485 16.03 0.7782 6.82 0.9747 8.11
Ages sq./100 -0.0818 -14.95 -0.0638 -14.04 -0.1196 -7.78 -0.1410 -9.11
Education(reference group is less than school cert.)
School certific. 0.0790 3.74 0.0925 4.41 0.5570 9.40 0.5827 9.17
bursary 0.1141 2.84 0.0955 2.47 0.7711 6.33 1.0253 7.97
Voc./trade cert. 0.1735 3.90 0.1173 2.80 1.0230 7.19 1.0304 6.90
Bach. Deg/dipl. 0.0340 0.47 0.0503 0.91 0.4215 1.58 0.8025 3.43
Post-grad. qual. 0.1337 1.08 0.0227 0.23 0.2524 0.52 0.7144 1.39
part deg/other 0.1469 2.70 0.1173 2.44 0.8809 4.58 0.9228 5.10
Pgrad*age/10 0.0672 2.05 0.0838 3.43 0.1815 1.43 0.1545 1.25
Bach*age/10 0.0684 3.13 0.0515 3.53 0.1116 1.35 0.0525 0.82
Voc/med*age/10 0.0045 0.39 0.0126 1.35 -0.0786 -2.15 -0.0545 -1.65
Ethnicity (reference group is European)
Maori/Pacif.Isl. 0.0183 0.57 -0.0070 -0.24 -0.3771 -3.79 -0.1190 -1.04
Maori/Pac.only -0.0484 -1.78 -0.0460 -1.77 -0.5688 -8.28 -0.4701 -6.22
Other non-Eur. 0.1799 1.62 -0.0955 -1.37 0.3182 0.57 -0.3550 -1.54
Other n.E. only -0.0800 -1.31     0.2516 1.03    
Pgr/bac*ma/pa -0.0200 -0.18 -0.0754 -1.15 0.7686 1.37 0.5963 1.66
Pgr/bac*other 0.0739 0.76 0.1009 1.17 -1.0607 -3.09 0.2014 0.57
voc/med*ma/pa -0.0241 -0.58 -0.0086 -0.21 0.1018 0.78 -0.0568 -0.40
Voc/med*other -0.1043 -1.17 -0.0448 -0.46 -0.7471 -2.23 -0.0996 -0.28
Industry (reference group is services)
agriculture -0.0161 -0.47 -0.0029 -0.06        
Mining/quarry 0.1353 1.33 0.2428 1.72        
Manufacturing 0.0608 3.17 0.0138 0.64        
Elec./gas/water 0.2305 4.32 0.0459 0.57        
construction 0.0078 0.30 -0.0293 -0.48        
trade -0.0541 -2.63 -0.0613 -3.90        
transport 0.0527 1.66 0.1354 3.82        
finance/real est. 0.0902 3.81 0.0452 2.62        
communication 0.1163 3.44 -0.0466 -1.31        
other 0.0775 1.51 0.0778 1.70        
Occupation (reference group is elementary occupations)
manager 0.2528 9.14 0.3438 10.47        
professional 0.2276 7.87 0.3280 10.63        
Associate prof. 0.2441 9.34 0.2738 8.71        
clerks 0.1453 5.17 0.2060 7.32        
Sales workers 0.0435 1.75 0.0640 2.23        
Agr./fish. wrk. -0.0655 -1.79 0.0069 0.12        
Trades workers 0.0644 2.95 0.1186 2.44        
plant/mach.wrk 0.0478 2.11 0.0553 1.53        
Elig. NZ super         -0.9071 -4.61 -0.5125 -3.90
Other inc./1000         -1.4714 -6.29 -0.8644 -5.14
Live w. parents         -0.2377 -4.87 -0.1605 -2.74
Region (reference group is Auckland)
North North isl -0.0918 -4.77 -0.0746 -4.13 -0.2774 -4.43 -0.2174 -3.23
Central N. isl -0.0834 -4.09 -0.0988 -5.30 -0.2842 -4.24 -0.0135 -0.19
Wellington -0.0212 -1.13 0.0351 2.16 -0.1182 -1.72 0.0335 0.49
Canterbury -0.0811 -4.15 -0.0790 -4.35 0.0045 0.06 -0.1048 -1.43
South island -0.0623 -3.28 -0.1144 -6.21 -0.1915 -2.83 -0.1295 -1.76
Year (trend) 0.0034 0.90 0.0083 2.38 0.0113 0.84 -0.0047 -0.34
Unempl. rate -0.0064 -1.23 0.0090 1.43 -0.0297 -1.65 -0.0617 -2.46
constant 1.1182 11.41 1.1303 11.64 -0.3980 -1.36 -0.7083 -2.11
Correlationa 0.3937 0.18,0.57 0.3906 0.20,0.55 Nr of obs. 4691   4279
Sigmaa 0.3301 0.32,0.35 0.2880 0.28,0.30 Nr of 1474   1461
Mill’s ratioa 0.1300 0.06,0.20 0.1125 0.06,0.17 cens.obs.      
Log likelihood         -3357.84 -2614.05    
Restricted Log likelihood b         -4736.79 -4043.03    
Pseudo-R2 c         0.28   0.34  

 

Notes a: Instead of a z-value a 95% confidence interval is given.

b: The restricted model consists of a wage equation with a constant and sigma and a selection equation with a constant only.

c: Pseudo R2 is calculated by 1 –

Table 3– Joint Wage and Selection Models, Sole Parents
  Wage equation Selection equation
  Coef. z-value Coef. z-value
  Wage equation Selection equation
  Coef. z-value Coef. z-value
woman -0.2104 -5.05 -0.0385 -0.39
age/10 0.1830 1.38 1.1312 4.02
Age sq./100 -0.0250 -1.47 -0.1556 -4.23
Education (reference group is less than school cert.)
School certific. -0.0669 -1.75 0.4041 4.92
bursary 0.0186 0.14 0.4286 1.36
Voc./trade cert. -0.0504 -0.37 0.5586 1.73
Bach. Deg/dipl. -0.1994 -0.73 1.2767 1.63
Post-grad. qual. -0.4273 -0.85 -1.5948 -1.07
part deg/other -0.0584 -0.40 0.4093 1.14
Pgrad*age/10 0.1701 1.52 0.5880 1.72
Bach*age/10 0.0774 1.13 -0.0957 -0.47
Voc/med*age/10 0.0208 0.62 0.0621 0.74
Nr of children     -0.0825 -2.23
Age of youngest child
0     -1.5800 -8.82
1 to 3     -1.1164 -8.98
4 to 5     -0.9182 -7.11
6 to 9     -0.6141 -5.84
Over 9     -0.3830 -3.49
Ethnicity (reference group is European)
Maori/Pacif.Isl. -0.0011 -0.02 -0.0924 -0.72
Maori/Pac.only -0.0221 -0.52 -0.2176 -2.55
Other non-Eur. 0.0441 0.34 -0.5945 -2.04
Pgr/bac*ma/pa 0.0374 0.21 -0.5981 -1.32
Pgr/bac*other -0.1301 -0.60 0.1989 0.34
voc/med*ma/pa 0.0673 0.89 -0.2719 -1.52
Voc/med*other -0.0216 -0.10 0.5881 0.98
Industry (reference group is services)
agriculture -0.0715 -0.73    
Manufacturing 0.0983 1.91    
Elec./gas/water 0.3698 1.84    
construction 0.1520 1.64    
trade -0.0167 -0.47    
transport 0.1775 1.82    
finance/real est. 0.1266 2.70    
communication 0.1618 1.90    
other 0.1492 1.40    
Occupation (reference group is elementary occupations)
manager 0.3217 4.81    
professional 0.4110 7.13    
Associate prof. 0.3394 5.58    
clerks 0.2022 3.86    
Sales workers 0.0683 1.35    
Agr./fish. wrk. -0.0287 -0.28    
Trades workers 0.0283 0.34    
plant/mach.wrk 0.0657 0.98    
Elig. NZ super     -0.3797 -0.47
Other inc./1000     0.1897 0.55
Live w. parents     0.2238 1.71
Region(reference group is Auckland)
North North isl -0.0577 -1.50 -0.2252 -2.45
Central N. isl -0.0992 -2.57 -0.0384 -0.40
Wellington -0.0388 -0.94 -0.0743 -0.70
Canterbury -0.0720 -1.75 -0.0323 -0.30
South island -0.0455 -1.02 -0.1434 -1.28
Year (trend) -0.0120 -1.52 0.0462 2.37
Unempl. rate -0.0197 -1.43 -0.0038 -0.11
constant 2.5031 7.60 -1.8147 -2.81
Correlationa -0.1600 -0.45,0.16 Nr of obs. 2166
Sigmaa 0.3309  0.31,0.35 Nr of censored obs. 1409
Mill’s ratioa -0.0530 -0.16,0.05    
Log likelihood     -1347.18  
Restricted Log likelihood b     -1798.08  
Pseudo-R2 c     0.22  

Notes a: Instead of a z-value a 95% confidence interval is given.

b: The restricted model consists of a wage equation with a constant and sigma and a selection

equation with a constant only.

c: Pseudo R2 is calculated by 1 – .

The interpretation of coefficients in the wage model is not as straightforward as in a simple linear regression. The effect of a one-unit change in a characteristic is calculated by using the following formula: [exp(relevant coefficient) – 1]×100%. For example, a married woman with a postgraduate degree is expected to be offered a wage rate, which is about 52 per cent higher than for a married woman without post secondary qualifications[10].

Notes

  • [10]In this example: [exp(0.4187)-1] ´100% =52.0% for married women.
Page top