A Wellington researcher in economic and public policy has confirmed what pay equity advocates already suspected about the gender pay gap in New Zealand - it's sexist.
Isabelle Sin said it was disappointing, "but not entirely surprising because we knew of this gender pay gap".
But what wasn't known was the pay gap persists, even when women are equally as productive as their male colleagues.
Ms Sin said we needed to face the facts that there is a problem.
"It's not just the industries that women are choosing to work in, it's not that women are less productive. It's sexism and it's not fair."
The research looked at the productivity and wages of men and women in private firms over a 10-year period, and found that despite women contributing just as much to their companies they are still paid less.
Women between the ages of 25 and 39 earn 16 percent less than their male colleagues, which jumps to 21 percent in the 40 to 54 age bracket and 49 percent for women.
This confirms what the Pay Equity Coalition has suspected for years.
Spokeswoman for the organisation, Angela McLeod, said they'd known this for a long time, "and yes, it's been anecdotal, however it's great to have the research to back up what we already know".
The difficult part was how to change it, she said.
A lot of the work that was being done to close the gender pay gap is focused on getting women into the workforce and into leadership positions.
But this research shows that once they're in these positions they're still not being paid as much as their male colleagues.
Ms Sin believes one of the reasons the pay gap has been able to persist was due to secrecy around wages, and said if employees disclose their pay to colleagues then women are in a better position to negotiate for pay equity.