The deadline for large employers to report their gender pay gap is now only one week away, and although the majority of companies are yet to report, the last month has seen some hair-raising pay gaps being reported by Easyjet, HSBC and others.

Companies are coalescing around a common defence of their pay gaps: women and men are doing different jobs, meaning a pay gap is unavoidable – and perfectly legal. In Easyjet’s case, for example, fully 94% of its airline pilots are men, while 70% of cabin crew are women. These jobs require substantively different training and levels of responsibility, and therefore it is entirely right that there should be a pay gap between the two types of work. The same reasoning is echoed in other statements issued so far: there are more men partners; traders; and senior managers, and they are inevitably (and rightly) paid more.

Does this mean we have nothing to worry about?

It is certainly true to say that the stratification of jobs by gender is more of a defence than, say, arguing that two people in equivalent roles actually had different responsibilities. It isn’t a result of illegal discrimination (necessarily). But it shouldn’t get firms off the hook if the problem is revealed to be more of an ‘occupation gap’, or even an attainment gap, rather than a pay gap.

Occupations may be stratified for various reasons, not all of which are as troubling from a gender equality perspective. Midwifery, for example, is a job overwhelmingly done by women, which is likely to be at least partly a consequence of more women than men being attracted to it as a career.

Other professions (and companies) are gender-imbalanced for less benign reasons, however: they are a consequence of a working environment that is, in various ways, inhospitable to women, meaning they join in smaller numbers, leave more quickly, and get promoted more slowly. This should be a concern to all employers keen to attract and retain the most talented individuals.

But it is about more than just organisational effectiveness: there are broader societal implications to a world in which our political leaders, investment managers and software engineers are predominantly male. Job stratification, where it occurs in influential places, alters outcomes, generally making them less favourable to the under-represented group. For example, artificial intelligence is being developed by a predominantly white male workforce of scientists and engineers, which has already resulted in algorithms that seem to display bias – of race and class as well as gender. Only by being actively involved in the development of AI will women head off the risk of inequality being ‘baked in’ to this and other new technologies.

Gender pay reporting should be a prompt to firms to step up their responses to a stratified workforce. Where the stratification is the result of a substantive difference in the skill sets required for different roles, as in the case of airlines, then firms should do what they can to make the boundary between different roles as porous as possible, including by subsidising retraining of the candidates who demonstrate potential. Easyjet is already doing something like this with its Amy Johnson initiative, which aims to increase the number of female pilots, but it could perhaps direct this assistance and support more towards its existing workforce.

To tackle the under-representation in senior roles where the problem isn’t necessarily one of different skills, firms need to use a range of interventions to attract, retain and promote women – and not all of them targeted at women. Encouraging more senior men to work flexibly and take time off for caring responsibilities, for example, would set a fantastic example to both men and women.

Enforced pay gap reporting has revealed that our gender pay gap has more subtle causes than we might previously have assumed. The challenge now is to ensure that firms respond by tackling it, rather than simply defending it.

Catherine Colebrook is Chief Economist at IPPR and Associate Director for Economy and Housing. She tweets @cath_colebrook.