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Women in physics


The percentage of women in post-graduate physics positions has stalled just below 20%. The most precipitous drop in women’s representation occurs between high school and university; however, women at all career stages struggle with ongoing cultural burdens and obstacles.

Quantifying the gender gap

In affluent countries, only approximately one-fifth to one-fourth of the students enrolling in a university undergraduate physics course are women (see Fig. 1). “Given that the United States isn’t the only country that’s hitting a 20-percent limit, I suspect that 20 percent is the number of women who are tough enough to bear it,” said Laura McCullough, a physicist at University of Wisconsin–Stout.

Fig. 1: Women remain under-represented in physics around the world at undergraduate, PhD and faculty levels.

Sources: American Institute of Physics, German Physical Society, Institute of Physics (UK), French National Center for Scientific Research and Chinese Physical Society.

To understand the extent and origin of the gender disparity in physics, reliable statistics are needed. Fortunately, many research institutions, universities, professional physics societies such as the Max Planck Society and Institute of Physics, and government agencies such as the National Science Foundation systematically collect data about their gender demographics and statistics. These organizations generally gather such data annually and, at least in the United States and the United Kingdom, they have access to high school student surveys every few years.

The International Union of Pure and Applied Physics (IUPAP), which organizes the International Conference on Women in Physics every 3 years, conducts global surveys of physicists, and one is currently underway. Its most recent survey, completed a decade ago, included respondents from more than 130 countries, though only 9 countries had enough women respondents for a statistical analysis, according to the American Institute of Physics (AIP). Furthermore, only three of those countries’ professional physics societies distributed the surveys to random samples of members or the entire membership, therefore, the data, although useful, are not completely standardized.

Such data are readily available in North America and much of Europe; however, it is more challenging for less affluent countries, where institutions often do not have the budget to periodically and comprehensively collect it. Data and trends in other regions sometimes turn out to be more uncertain.

Researchers have found evidence for regional variation, including some surprises. In particular, many Middle Eastern and Eastern European countries, such as Iran and Romania, are doing better than the United States, Canada and central European countries1. The latter have lower percentages of women in physics and other science fields, even though they have higher absolute numbers. This may be due to a different salience of gender-based stereotypes that influence students as they pursue their studies and consider careers in science.

Reasons for early career choices

Social scientists who study gender disparities in physics and other science fields have also begun to look into students’ aspirations for physics and maths before they decide whether to continue with them — that is, before the fraction of women declines far below 50%. For example, Maria Charles, a University of California Santa Barbara sociologist, assessed the responses of eighth graders in 32 countries to the statement “I would like a job that involved using math.” She found that not only are women in rich countries like Australia, Italy and Japan less likely to work in these fields, but they are also half as likely to aspire to them. She hypothesizes that this is related to people’s views about the meanings of careers. “In affluent countries, we’re constantly told to do what we love and follow our passions. But eighth graders don’t necessarily know what they love or what they’re good at, but they will tend to rely on gender stereotypes. That could mean that there is a stronger penetration of these stereotypes into the process of career selection,” Charles said.

Beyond the bachelor’s degree and doctorate, women’s representation drops further at the level of faculty positions and other permanent jobs. In both the United States and much of Europe, the fraction of physics faculty who are women stands at 16%, on average, according to the Gender Equality Network in the European Research Area (GENERA).

Physics is hardly the only field of science, technology, engineering and math (STEM) with gender disparities, but it is one with particularly large gaps between men and women. Physics, computer science and engineering consistently lag behind other fields, with approximately 5% fewer women PhDs and faculty than in astronomy and approximately 10% fewer than in mathematics and chemistry, according to AIP data. Sociologists have observed that men tend to be over-represented in high-prestige fields; however, in many (though not all) countries, physics achievements are widely viewed as prestigious.

For computer science, it wasn’t always this way. Women used to comprise 34% of computer science undergraduate degree holders in the 1980s, but that fraction has declined dramatically since then. “My theory is that as the status of the field has increased, the number of women has gone down,” McCullough said. Research shows that when people think that success in a field depends on some kind of innate ‘brilliance’ or even ‘genius’, rather than hard work and skills developed over time, it leads to more gender segregation and lower numbers of women. This especially seems to play out in physics, computer science and philosophy. A 2017 study2 found that 6-year-old girls already avoid activities said to be for “really, really smart” children, and they’re less likely than boys to associate members of their gender with that trait.

Views about the culture and purpose of a field matter too. When people view physicists as geeky and socially isolated, those traits are associated more with men, and it makes women feel like they don’t belong. In addition, Indiana University psychologist Amanda Diekman finds3 that more women than men have communal goals — they want to work with people and help people — and a lot of students do not see physics as something they can achieve such goals with.

Inequalities persist through careers

Gender stereotypes and cultural biases seem to be decisive factors in early career choices. At later stages, however, women have to contend with inequality in salaries and unequal access to resources and opportunities to do and present their work.

“If you can’t change an unequal situation, people won’t want to get into it. If you can’t fix that kind of inequality, it doesn’t encourage people to stay in the field,” said Rachel Ivie, head of the Statistical Research Center at the AIP in College Park, Maryland. She finds that women accumulate 30–50% fewer resources such as funding, office and lab space, equipment, clerical support and students than men in Canada, China, Italy, Spain and the United States. In China, France, Italy, Japan and Spain they accumulate similarly fewer opportunities such as giving talks as an invited speaker and serving on committees for grant agencies. Women also have fewer opportunities to be lead authors on research publications and are treated worse in recommendation letters and by hiring committees4,5,6.

Important and relevant inequalities persist outside of the lab too. For example, Ivie finds that men in Japan and Germany are more likely than those in other countries to say that having children did not affect their careers. She also cites other research showing uneven distributions of housework, with men in Italy and Japan doing much fewer household duties than their spouses. Cultural expectations about who does child-rearing work affect women’s work–life balance and inevitably take a toll, she argues. This occurs in the United States as well7, where nearly twice as many women as men leave science careers after having a child. On top of this, women frequently have to deal with sexual harassment. In a 2018 report8, the National Academy of Sciences highlights surveys showing that at least 20% of female science undergraduate and graduate students experienced sexual harassment from faculty or staff. The authors argue that there is a perceived tolerance for such harassment in academia, and that academic institutions should move beyond legal compliance to address their culture and climate.

Closing the gap

To close the gender gap, the issues occurring at both the very early and later career stages must be tackled. For example, a group of United States institutions, led by Zahra Hazari at Florida International University, have developed Step Up For Women. It is a programme that provides high school teachers with materials, including lesson plans about career goals and profiles of women who have achieved myriad careers with their physics degrees. It is designed to support women who might be interested in physics but don’t realize it or do not have the confidence yet to pursue it. “High school is the key time because that’s when students are deciding what they’re going to major in. If we intervene earlier, they might forget what we tried to do with them, and after high school it’s too late,” said Robynne Lock9, a physicist at Texas A&M University-Commerce.

French researchers have also recently experimented at the high school level, performing 1-hour-long interventions with classrooms of 10th and 12th graders in 98 schools in the Paris region. Volunteer female scientists visited classrooms and presented slides and videos that described gender stereotypes in science and that debunked myths about science careers. After the treatment, the participation of female students in math, physics and engineering programmes increased by 20%. “At least you have some evidence that the role model matters. It’s also a light touch and potentially cheap intervention,” said Clémentine Van Effenterre, a Women and Public Policy Program fellow at the Harvard Kennedy School and co-author of the study10.

Because the biggest drop in the fraction of women in physics occurs between high school and university degrees, the AIP is trying to probe reasons for that decline. They have begun a 5 year “persistence and attrition” study that follows incoming university students and assesses who majored in physics, who stayed in physics and who completed their degrees. “We have some evidence that women were more likely than men to say that a particular university professor or class influenced their decision to major in physics,” Ivie said.

In developed countries, women more often cite childcare as an obstacle to pursuing a career in physics. In France, for example, with available and affordable childcare, women make up a higher percentage of physicists than in Germany, where it is more difficult.

Throughout Europe, the GENERA Network has agreed upon a new memorandum of understanding with at least 20 universities and research organizations, including in France, Germany and Italy, that commits them to regular data collection. They also provide training activities that encourage gender-sensitive hiring processes, review panels and decision making. “It’s rather important if you want to change something that management is behind it,” said Thomas Berghöfer, coordinator of the GENERA project.

All these researchers hope that, following such interventions, programmes and activities, in a few years the currently low percentages of women with physics degrees and in physics jobs in the United States and central Europe will finally begin increasing again. They will inform future interventions that could one day push physics toward gender parity.

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Change history

  • 28 May 2019

    An amendment to this paper has been published and can be accessed via a link at the top of the paper.


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Correspondence to Ramin Skibba.

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