Overall, men earned more than women at all qualification levels by five years after study - with a difference of more than $10,000 for those with a masters degree.
Women's earnings were 92 per cent of men's after completing a bachelors degree, 84 per cent after a masters degree and 85 per cent after a doctorate.
The report's author, Paul Mahoney, noted that as well as any differences in pay rates, earnings could be affected by differences in preferred occupations and hours worked - all of which the study did not measure.
But a spokeswoman for the Pay Equity Coalition, Angela Mcleod, told the Weekend Herald the report followed research that showed a difference in pay on an hourly basis.
There was structural discrimination and unconscious bias in workplaces, she said, and the solution was to fight on a number of fronts, including in the courts - a landmark equal pay case is under appeal - and through education.
Another strategy is recognising companies that are moving to close the gender pay gap. The YWCA Equal Pay Awards will acknowledge firms which have implemented equal pay policies or are taking meaningful action.
In the public sector, Equal Employment Opportunities Commissioner Jackie Blue has promised action after her analysis found women were paid an average 14 per cent less than their male counterparts.
Yesterday's report, which used data from Statistics NZ and Inland Revenue, also found that men are more likely to head overseas after study. That difference varied between qualification level and study area. People with higher qualifications were more likely to look abroad.
Almost two-thirds of men who completed natural and physical sciences doctorates were overseas five years later, compared with 28 per cent of women.
