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.