Women’s work has been systematically undervalued for far too long. Now the scale of the problem cannot be denied

To know the scale of a problem is not always to know its nature, but it is a start. Thanks to data published ahead of a midnight deadline on Wednesday, a clearer picture is emerging of the extent to which British women are systematically paid less than men.

This finding reinforces the story told by equivalent public sector data published to a deadline last week. The picture is still incomplete. Only firms with more than 250 employees are compelled to release their data and some have produced numbers that don’t add up. Hundreds left it until the very last minute to comply, suggesting embarrassment, hope of avoiding scrutiny or a casual attitude to the whole issue.

Organisations should want to close their pay gap, not to avoid shame but because a workplace that denigrates the contribution of its female staff errs on commercial as well as ethical grounds. Exploitation – and that, ultimately, is what this is about – demoralises workers and chases away talent.

Analysing the data will take time, but the pattern is clear enough. About 78% of companies report a median-wage disparity in favour of men. Some sectors are worse offenders than others, with construction and finance companies looking especially unequal – with median hourly wage gaps often over 20%. Of companies that reported on the final day, Ryanair stood out. Median hourly pay for women employed by the airline is 71.8% lower than for men.

According to the Office for National Statistics, the average pay gap for the UK last year was 18.4%. Doubtless the Equal Pay Act, nearly 48 years old, is still being flouted in some cases. But the principal problem is too few women in the highest-paying roles. That raises a new set of questions about the obstacles to advancement through male-dominated hierarchies.

A pay gap between women, clustered at the lower end of the scale, and men, nearer the top, is also symptomatic of a broader problem with pay ratios. The chief executives of FTSE 100 companies earn, on average, about 120 times more than the national median wage of a full-time worker.

Theresa May has spoken of inherent unfairness in a system that allocates reward so unevenly. Ahead of today’s deadline she described the specific problem of gender pay gaps as a “burning injustice”. The prime minister rightly also highlighted the problem of millions of women not being paid at all: nine out of 10 people who are kept out of the labour force due to caring duties are women. And it is no coincidence that paid carer roles, disproportionately filled by women, are among the lowest paid. The prejudices that limit and undervalue women’s participation in the economy run deep.

The prime minister’s attention to this cause is welcome, although, as in other matters of economic justice, she is more energetic with rhetoric than action. The mechanism that has exposed the gender pay gap is not speeches but law.

Invitations to voluntary change are easily rejected. And it is human nature for the beneficiaries of any bias to imagine that their privileges are fairly earned.

That is why evidence of a systemic imbalance is so vital. Sight of the scale of the problem should make it impossible to ignore, although the cavilling tone and the excuses offered by some companies suggest reluctance to face the facts. It will take sustained public and political pressure to effect change, ensuring that denial is no longer an option.