Australian businesses need to adhere to a healthy work hour limit for the mental health of workers and to take into account the amount of caring work women do at home, our research shows.

More than 80 years ago, when most paid jobs were worked by men, the International Labour Organization (ILO) set the work week limit to 48 hours a week. This was based on evidence that long work hours are bad for health. Since then, the labour market has changed. Almost half of the workforce is made up of women and two-fifths of employed adults hold down a job while caring for children or elderly parents.

Employers in Australia should honour the current 38 weekly hours set by the National Employment Standards. But more than 40% employed Australians work more than 40 hours per week at the moment.

We modelled work hour limits and what happens to mental health when they are exceeded using data from 3,828 men and 4,062 women aged from 24 to 64, as part of the Household, Income and Labour Dynamics in Australia (HILDA) Survey. Our findings showed that on average, the maximum number of hours that can be worked before mental health starts to suffer is 39 hours. We did this by looking at the reciprocal relationships between work time, mental health and wage in our modelling. This 39 hour threshold is a full nine hours less than the ILO’s 48-hour-week.

However, the average working hours in a week hides an important gender difference.

The differences between men’s and women’s working hours

Women usually spend more time caregiving and have very different experiences on the job. This is because they have lower pay and less paid leave entitlement.

Women are still working in a labour market that systematically disadvantages them in terms of pay, conditions and rewards. Women have less autonomy than men and they earn 17% or $277.70 less per week on average, full time. Hour for hour, women get less.

These differences don’t reflect any natural difference between men and women. We know that women are as educated and as skilled as men.

The playing field is not level and this affects work hour limits. When systematic differences in resources and rewards on and off the job are also taken into account, our study shows the work hour limit widens further to 34 hours for women compared to 47 hours for men.

This gives men a 13 hour time advantage on the job, largely because they spend much less time on care or domestic work than women. Only if women were to spend very little time on care or domestic work, and if they had the same resources and rewards on and off the job, would the work hour limits converge.

Under these assumptions men and women without care responsibilities can work up to 48 hours before their mental health is affected. However, anyone who spends significant time caring for others or doing domestic work is unable to work long hours without facing a likely health trade-off.

The hour glass ceiling is self perpetuating

Our study reveals that current limits and assumptions about how long Australians should work if they want a “good” full time job is systematically disadvantaging women’s health.

Men dominate the workforce with long working hours – these jobs are often paid the best. This creates an expectation of working long hours if you want a good job.

This is no longer feasible or fair for a majority of Australian households, both adults now need to work, locking women into short part time hours in order for households to manage. We show that if men were to do more of the caring then their work hour limit also lowers. So the way our job market is at the moment is a problem for men who want to contribute more to care and domestic activities.

In contrast to this, in Finland, the vast majority of men and women both work full time, with lower average work hours and less of a gap between the sexes (40 hours for men, 38 for women). Not surprisingly Finland outperforms Australia on most gender equality indicators.

Australian employers need to continue support women to be employed and to earn equal pay, for example with good quality childcare and reducing sex discrimination in the workplace and beyond. But employers also need to support men to give time to care without suffering a job or pay penalty.

Australia also needs to tackle the widespread belief that it is fair or feasible for people to work long hours without compromising either their health or gender equality.

Lyndall Strazdins receives funding from The Australian Research Council and the National Health and Medical Research Council.

Huong Dinh and Jennifer Welsh do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.