Award-winning feminist campaigner and author Caroline Criado Perez remarks that what has changed in the 21st century are the ways in which women continue to be seen as the "other". Her book, Invisible Women: Exposing Data Bias in a World Designed for Men illustrates what the Gender Data Gap is and why we need to recognize it as the world becomes more reliant on data and technology.

Most of recorded history has a data gap. Starting with the theory of Man the Hunter, there is no mention of women’s role in humanity’s evolution. Instead, the lives of men have been taken to represent those of humans overall. This has created a huge gender data gap in the representation of the other half of humanity. The modern world is riddled with elements designed with little to no consideration for women. City planning, economic policies, technology, medical treatment, tax structures – they are all defined by the absence of data for women and have thus, inevitably, been designed for men.

The book begins by differentiating "sex" from "gender" and explains their significant consequences for women as they navigate a world constructed on male data.

Women do 75 percent of the world’s unpaid work, in addition to paid work, and this affects their travel needs. Shopping for groceries, dropping kids off to school, caring for the elderly – these responsibilities require women to travel, making them more likely to use public transport, which public utilities fail to consider.

On average, 61 percent of daily housework is done by women. As per a UK study, men enjoy up to five hours more leisure time per week after work as compared to women. Even when men increase their share of unpaid work, they are unlikely to take up the messy, personal, emotionally draining aspects.

Research has shown that manufacturers fail to account for sex-disaggregated user data, thus creating products that are difficult to use. From heavy agricultural hand-tools to large smartphones, from apparel to interior design, from musical instruments to voice recognition software, product design is based on the default male while women are expected to accommodate.

Medicine has always functioned on the assumption that male bodies represent all humanity. There is an ever-increasing data gap on how symptoms, diseases and treatments affect female bodies due to which women are being diagnosed incorrectly and are dying.

Unpaid labour is not simply a woman’s job. It is an activity which benefits all of society and pushes the economy. However, it is also something that eats away into time that women could spend in paid labour which is known to have a significant impact on the GDP. Unfortunately, their low percentage of participation in paid labour force also brings about a gender pay gap and this in turn has helped evolve a tax system that disincentivises women to enter paid employment.

The irony of excluding women’s voices is that in extreme contexts women are disproportionately affected by conflicts, disasters and pandemics, which impacts their health, safety and freedom.

The observations in the book make it evident that by failing to collect data on women, we are continuing to naturalise sex and gender discrimination. Therefore, it is imperative to increase female representation in all spheres of life. As more women move into positions of power or influence, they ensure that women are not forgotten, that they are brought out of the shadows and can speak up and be heard which is to the benefit of all humanity.