The gender pay gap would be tighter if men took more time off work, a new report has claimed.
UK thinktank the Institute for Public Policy Research (IPPR) says the disparity between men and women's pay is largely down to the fact men hold more senior positions, partly because they tend not to take time off when they become dads.
"Even with shared parental leave now an option, it is still women who will typically take a longer time away from work in order to look after children," the State of Pay report says.
"This career break, even if short, can mean the loss of development and progression opportunities."
In 2015 the UK changed its parental leave rules, allowing mums and dads to split the leave between them, including the paid leave - even at the same time, if they wish.
But shared parental leave has only been taken up by 2 percent of those eligible, the report says, and when women do return to work, it's often only part-time or at a lower-level position to retain flexibility.
"The pay gap opens up at the age of 40 - the period when the demands of childcare are at their height - and persists for the remainder of a woman's working life," the report states.
"Reducing the gender pay gap there requires an equalisation of the lifetime hours that men and women work, through both better return-to-work policies, and more men taking time out of the labour market and working flexibly, to distribute caring responsibilities more evenly."
The report notes it's often the woman who takes time out because her earnings are less than that of her husband, even before having children.
"Changing men's working behaviour is a crucial component of equalising pay," report co-author Catherine Colebrook told The Guardian.
"Employers could offer paid paternity leave on a 'use it or lose it' basis, make jobs flexible by default and encourage men to job-share."
Another suggestion in the report is for employers to make sure current employees are paid at least as much as any new recruits, so women aren't forced to ask for more pay. Studies have shown they are less likely than men to push for higher salaries.
A third is that companies don't negotiate salaries at all, so men aren't even given the chance to get ahead of their female colleagues.
The full report can be read on the IPRR website.
In New Zealand it is possible for the man to take both the unpaid parental leave he's normally entitled to, and the paid leave that would normally go to the mother, but they both can't take it the same time.