While computing began as a field heavily dominated by women, this changed in western countries shortly after World War II. In the US, 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 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.