Imagine working long hours day in day out, falling into bed exhausted each night and getting up with the sun each morning — but never getting paid and never, according to the people who measure such things, actually “creating value”. It sounds grossly unfair, but this is the condition of most women around the world. When governments measure national economies in the gross domestic product, “women’s work” — caregiving, housekeeping, home-making — does not count as “work”.

Thanks to a new report out from McKinsey on the gender gap in the workplace, though, we now know the actual value of all this unpaid work: a staggering $10tn. That is roughly the size of China’s GDP. If all the women taking care of their families constituted one nation, it would have the fourth-largest economy in the world.

All this work, moreover, is just the physical dimension of care. As Anne-Marie Slaughter argues in her new book, Unfinished Business , caregiving includes the additional emotional component of love and nurture, the transformation of an income stream into the teaching, discipline, moral guidance, problem-solving, emotional support and role-modelling that raising children and simply investing in others requires. That is work worth measuring.

These inequities exist in rich and poor countries alike. In rich countries, women turn money into the goods and services necessary for survival and flourishing: shopping, cooking, cleaning, washing, organising. In poor countries, women bear the burden of providing the basic necessities of life: hauling water and firewood, and farming subsistence crops.

We must act. The economist Diane Elson has created a strategy that has been adopted by many advocates: “Recognise, reduce and redistribute.”

Recognising the unfair burden being placed on women is the first step to addressing it. As long as economic statistics of record erase the work they do, it will be easier for everyone to ignore the disparity at the heart of our societies.

Reducing the amount of time and effort women spend doing tedious chores is possible with labour-saving technologies. In developing nations, where women spend hours gathering water and wood to run their households, this may mean efficient cookstoves, community cisterns and rural electrification. In richer countries, we have been using washing machines, electric irons, and vacuum cleaners for years. By reducing the 61 per cent of unpaid work that consists of routine household tasks, we can free up time for the valuable work of caring for children and elders.

Redistributing unpaid labour, the last step, means including men equally in the work and the joys of care. Men who bond with their children early on and become fully competent at childcare report that they experience a different and deeply fulfilling relationship. Moreover, when men and women are equal co-parents, they are both likely to push for the flexible work arrangements that would help everyone.

We do not know with certainty what women will do with the extra time they gain from reducing and redistributing unpaid work. But it is hard to imagine they would not use some of it for economically productive activities or to further their education. That is where a second number in the McKinsey report comes in: if the world’s women were not assigned the majority of household tasks, forced to take part-time jobs to accommodate childcare and other important responsibilities, or shunted into low-paying professions, global GDP would grow by a breathtaking $28tn, a number larger than the US and Chinese economies combined.

Estimates are tricky and real equality would mean men stepping back as women step up. Still, the business case is clear. Politicians, employers, investors, and voters have no excuse not to act.