Saudi Arabia's Vision 2030 economic reform and modernization plan says women are a "great asset" and vows to "develop their talents, invest in their productive capabilities and enable them to strengthen their future and contribute to the development of our society and economy."

Kevin Brennan, the shadow arts minister, said the situation was “not good enough” and called for a change in policy. “Only about a quarter of the work acquired by the government art collection in recent years is by women,” he said. “Female artists are at least as talented as their male counterparts and the government should be setting an example by getting rid of the institutionalised bias in their acquisitions policy.”

2017 may have been the year of feminism, but next year is shaping up to be a glorious year of female magnificence. Because the London Underground is going to be celebrating female artists all year, with a programme of works by women. The programme marks 100 years since women were granted suffrage. And it also forms part of Sadiq Khan’s gender equality campaign, #BehindEveryGreatCity, which hopes to celebrate the capital’s role in securing votes for women and looks to increasing gender equality in 2018.

Iran has opened its first museum dedicated to a solo female artist – Monir Shahroudy Farmanfarmaian, who has received widespread international attention during decades of exile. The nonagenarian doyenne of Iranian art and friend of Andy Warhol, Jackson Pollock and Willem de Kooning, had her first US solo museum exhibition at the Guggenheim in New York in 2015.

Visiting museums while growing up, Zolzoya Bakthuyag, a 34-year-old lawyer, always wondered why the places that depicted the history of her country always exhibited men’s photos and paintings so prominently. “Mongolian women played a great role building the country too, but museums only hang men’s photos. It was confusing,” she said, sitting in her office in a high-rise building huddled by snow-peaked green hills in the Mongolian capital Ulaanbaatar.

"People are very hungry for an open public discussion about what has occurred, why it occurs, and what can be done to affect change that really works," said the letter's organizers. "The letter was a rallying cry, to publicly speak out about a problem endemic to not only the art world, but the world at large."

The project alerts the public to the number of female artists in their cities, many of whom are invisible, the artists said. “Seeing is believing. You have all these curated shows of female artists, and curators stand up and say there were so many more artists. Okay, but how many more?” she said. “If you hold up a discrepancy, point it out, people have to confront it.”