The women whose words are tackling Wikipedia's male bias

Packed into the back room of a feminist bookshop in Madrid, 17 women hunched over their laptops, chatting and laughing as they passed around snacks. Every now and then a hearty burst of applause punctuated the sound of typing, each time marking a milestone as the group chipped away at what is perhaps one of the world's most pervasive gender gaps.

- Ashifa Kassam

Just under a fifth of Wikipedia's content, including biographies, is focused on women, while women account for just about 15% of the site's volunteer editors. "The numbers are pretty terrifying," said Patricia Horrillo, who for much of the past decade has spent her spare time working to tackle this gap, cultivating a community of Wikipedia editors dedicated to publishing content focused on women.

The result is Spain's Wikiesfera, one of a handful of groups - from Whose Knowledge? in the US to Italy's WikiDonne and Switzerland's Les Sans Pages - that have sprung up to address Wikipedia's gender balance.

It is something that has long been recognised by the Wikimedia Foundation, the organisation that hosts Wikipedia. "Wikipedia is powered by humans, so it is vulnerable to human biases," the foundation said. "It is also a reflection of the structural and historical inequalities women experience around the world."

Wikipedia has historically been edited by more men than women, all of whom rely on existing published sources to verify the facts in its articles, the foundation notes. "But in many places around the world, women have been left out of historical narratives and traditional sources of knowledge."