The day has been celebrated in some way for more than a century but was formally adopted by the United Nations in 1975. Since then, it's become a day to campaign for the equal rights of women from addressing domestic violence and sexual violence prevalence to safe access to terminations.

There's been much progress since its formation - the majority of women around the world now have the right to vote and work and can occupy leadership positions. But through all the strides forward, other areas have been tougher for women to break through.

One of those persisting issues is the gender pay gap.

Simply put, the gender pay gap is the difference in the average earnings between men and women and is used to measure the economic standing of women in society when compared to men.

It calculates how much more men are earning when compared to women and presents it with a simple percentage figure.

The bigger the percentage difference, the more barriers that stand in the way for women to achieve income equality.

READ MORE:

In Australia, the Workplace Gender Equality Agency (WGEA) calculates the gap using data from the Australian Bureau of Statistics on average weekly earnings.

The agency's most recent figures, as of November 2020, show Australia recorded its lowest gap at 13.4 per cent with women earning on average $242.90 a week less than their male counterparts.

As the gender equality agency noted, there are a number of factors that come into play.

For starters, women typically dominate traditionally lower-paid industries, such as healthcare and education.

Other factors can also include more caring responsibilities and a larger share of domestic work coupled with a lack of workplace flexibility to accommodate for it.

There are also the more nefarious reasons, including conscious and unconscious discrimination and bias against hiring and promoting women.

But it's further complicated by the fact the agency's data relies solely on full-time earnings.

The year's reporting was affected by the economic effects of the COVID-19 pandemic. The restrictions forced many businesses to close for extended periods of time, leading to a flow-on effect that saw big job losses.

It's suspected women will face the toughest road back to employment with new data from the Australia Institute indicating many had since returned to the workforce in part-time and casual roles instead.

The gender equality agency's director Libby Lyons said while the recent gender pay gap figure was promising, it did not signal a real-world improvement.

"As the nation's [COVID] recovery progresses, we may well see male wages increase with little or no positive improvement in the wages of women," Ms Lyons said.

"If this happens, it is feasible that the gender pay gap will increase.

"It is also important to highlight that this figure does not consider the number of women and men who are under-employed, that is those who have left the workforce or have had their hours reduced."

While the national gender pay gap stands at 13.4 per cent, some industries are worse than others.

According to WGEA, the highest gender pay gaps exist in professional, scientific and technical services at 24.4 per cent while finance and insurance services trailed closely behind at 23.6 per cent.

Healthcare and social assistance ranked third with a gap of 21.2 per cent.

By contrast, the industries recording the lowest gender pay gaps included public administration and safety along with retail at 6.3 and 8.7 per cent respectively.

Beyond industries, the gap varies depending on where you live too.

The ACT has the lowest gender pay gap at 6.3 per cent, which the agency attributes to having a large public sector workforce.

Western Australia has the country's highest gender pay gap at 22.9 per cent, a full 9 per cent more than the Northern Territory at second place.

The state's large mining and construction industry, which typically pays higher salaries and employs less women, is deemed a major factor behind the high gap.

The gender equality agency records pay gap data from non-public sector organisations with 100 or more employees and publicly publishes a report to reflect the figures.

The data represents around 40 per cent of the country's employees but politicians are promising to do more.

Opposition leader Anthony Albanese pledged on Monday a Labor government would audit the gender pay gap within the public service and require private companies to publicly report their gender pay gap data.

"The Commonwealth cannot ask the private sector to do something without showing leadership ourselves," Mr Albanese said on Monday.

"Under a Labor government, we would have an audit across all of the departments of the Australian public service, using the workplace gender equality agencies tools in the first year to identify exactly where these issues are."

Mr Albanese said the public reporting mechanism would be gradually introduced over a four-year period, beginning with companies employing more than 1000 workers and leading to those employing 250 or more.

"The first step is accountability and transparency. If you had that, what you would have his pressure on the companies to do something about it," Mr Albanese said.