Universities are an environment in which people like to have metrics for performance. Teaching has end-of-term questionnaires to students. Research has both papers published and grant money attracted. They are all very numeric factors that can be evaluated and compared between colleagues and between institutions.
If one institution strives for fighting the gender unbalance, it will open itself to performing worse on the metrics designed to suit men better. There are many indications for this. See, for example: unpaid work done by women, how much unpaid work is done by women, and especially @viglione2020Are women publishing less during the pandemic? Here’s what the data say. Also @alshebli2020The association between early career informal mentorship in academic collaborations and junior author performance has some data showing that women's work is less visible than men's also when acting as mentors.
Therefore, the efforts of hiring more women in universities cannot be sustained if people keep looking over and over again at the same metrics. One may argue that having more women may help changing the metrics used. Perhaps. But academia is a volatile environment, with a lot of transfers and international movement.
If one institution (or one country) adopts only hiring policies, the women will have no other place to go. If on the other hand, they skew the metrics so that women can get equal access to grants and publishing that is a long term career paradigm shift.
Surprisingly this is within reach: the hidden power of individual reviewers.
See also: Gender unbalance in academia
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