That means from today, UK women (collectively, effectively) stop being paid, based on the gender pay gap.
It means women have to work for 39 more days, just to earn what men do – because our average hourly pay is lower.
Alongside gender, class also has a huge impact on people’s pay, as well as their chances of building a better life for themselves and their families.
As deputy chair of the Social Mobility Commission, I’m proud of the work we have done this year to highlight the stark challenges women, and particularly women from less privileged backgrounds, face in achieving upward social mobility.
Our recent State of the Nation report analysed social mobility outcomes by sex for the first time.
We found that across all socio-economic backgrounds, women outperform men when it comes to educational attainment, and are more likely to attend university.
However, once men and women enter the workplace, this reverses.
Across all socio-economic backgrounds, women earn less than their male counterparts, are less likely to be in higher professional jobs, and are more likely to be economically inactive.
Each year, only 8% of women move from a lower working-class background to a higher professional occupation compared with 14% of men and women are underrepresented in higher professional jobs such as doctors and lawyers.
Among people with higher professional parents, 40% of men become higher professionals themselves compared to just 27% of women and women are more likely to experience long-range downward mobility (going from higher professional to lower working class jobs in their lifetime).
Hope still exists, however, as while the challenge is significant, it is not insurmountable.
Proper data collection and analysis is vital in allowing us to ascertain and understand the problem, and to consider how we might influence government policy to address and solve it.
But alongside this, we need to see a concerted effort from employers who play a key role in influencing and shaping an individual's social mobility outcomes.
Employers decide how their opportunity pie is divided up, they decide where jobs are located, and how their recruitment and promotion processes work. All of these factors directly dictate people's social mobility chances, outcomes and pay.
Employer decisions around pay and promotion impact living standards, spending power, and the health and wellbeing of employees and their families.
With over 30 million people in the UK in paid employment, the sphere of influence employers have is extensive.
We know from a growing body of evidence that addressing social mobility – and securing equal pay – is not just about who gets into a workplace; but also who gets ahead in it.
The research thus far shows that people from lower socio-economic backgrounds are not progressing as quickly as others.
Whether this is due to affinity bias and decision-makers tending to hire in their image or because people lack family connections and advantage, we cannot, and should not, stand by when we know that a person’s background is causing them to be held back from success.
Turning back to women, inequalities associated with different demographic characteristics rarely operate in isolation. Instead, inequalities tend to build on each other and work together.
For example, our State of the Nation research shows that in Britain’s higher professional and managerial occupations, women from working-class backgrounds face a double disadvantage in terms of earnings with young women from lower working-class backgrounds earning only 87% of their male counterparts’ earnings.
In addition to this, one of the most striking examples of the interplay between sex and socio-economic background is support after maternity leave where mothers earning less than £20,000 per year are more likely to not receive support returning to work than mothers on higher incomes.
The Fawcett Society found mothers on lower incomes were also less likely to secure flexible work arrangements, regular check-ins with senior managers, encouragement to prioritise training or development opportunities.
This in turn has a knock on impact on their ability to move into better roles and take up career opportunities.
So, on this Equal Pay Day, please also remember the class pay gap – and how we must all play our part in creating a United Kingdom where the circumstances of a person’s birth do not determine their outcomes in life.
Resham Kotecha is deputy chair of the Social Mobility Commission