While computing began as a field heavily dominated by women, this changed in western countries shortly after World War II. In the US, recognising software development was a significant expense, companies wanted to hire an "ideal programmer". Psychologists William Cannon and Dallis Perry were hired to develop an aptitude test for programmers, and from an industry that was more than 50% women they selected 1400 people, 1200 of whom were male. This paper was highly influential and claimed to have "trained the industry" in hiring programmers, with a heavy focus on introverts and men. In Britain, following the war, women programmers were selected for redundancy and forced retirement, leading to the country losing its position as computer science leader by 1974.
Popular theories are favoured about the lack of women in computer science, which discount historical and social circumstances. In 1992, John Gray's Men Are from Mars, Women Are from Venus theorised that men and women tend to differ in ways of thinking, leading to them approaching technology and computing in different ways. A significant issue is that women find themselves working in an environment that is largely unpleasant, so they decline to continue in those careers. A further issue is that if a class of computer scientists contains few women, those few can be singled out, leading to isolation and feelings of non-belonging, which can culminate in leaving the area.
The gender disparity in IT is not global. The ratio of female to male computer scientists is significantly higher in India compared to the West, and in 2015, over half of internet entrepreneurs in China were women. In Europe, Bulgaria and Romania have the highest rates of women going into computer programming. In government universities in Saudi Arabia in 2014, Arab women made up 59% of students enrolled in computer science. It has been suggested there is a greater gap in countries where people of both sexes are treated more equally, contradicting any theories that society in general is to blame for any disparity. However, the ratio of African American female computer scientists in the US is significantly lower than the global average. In IT-based organisations, the ratio of men to women can vary between roles; for example, while most software developers at InfoWatch are male, half of usability designers and 80% of project managers are female.
In 1991, Massachusetts Institute of Technology undergraduate Ellen Spertus wrote an essay "Why Are There So Few Women in Computer Science?", examining inherent sexism in IT, which was responsible for a lack of women in computing. She subsequently taught computer science at Mills College, Oakland in order to increase interest in IT for women. A key problem is a lack of female role models in the IT industry, alongside computer programmers in fiction and the media generally being male.
The University of Southampton's Wendy Hall has said the attractiveness of computers to women decreased significantly in the 1980s when they "were sold as toys for boys", and believes the cultural stigma has remained ever since, and may even be getting worse. Kathleen Lehman, project manager of the BRAID Initiative at UCLA has said a problem is that typically women aim for perfection and feel disillusioned when code does not compile, whereas men may simply treat it as a learning experience. A report in the Daily Telegraph suggested that women generally prefer people-facing jobs, which many computing and IT positions do not have, while men prefer jobs geared towards objects and tasks. One issue is that the history of computing has focused on the hardware, which was a male dominated field, despite software being written predominantly by women in the early to mid 20th century.
In 2013, a National Public Radio report said 20% of computer programmers in the US are female. There is no general consensus for any key reason there are less women in computing. In 2017, an engineer was fired from Google after claiming there was a biological reason for a lack of female computer scientists.
Dame Stephanie Shirley using the name Steve Shirley addressed some of the problems facing women in computing in the UK by setting up the software company Freelance Programmers (later F.I, then Xansa now Steria Sopra) offering the chance for women to work from home and part-time work.