Bielefeldt herself landed in engineering almost by accident. She was a "painfully shy" high school student in need of a summer job, she said, and too shy to walk into a mall. But an eight-week engineering research program at Iowa State University required simply filling out an application -- read: no talking required. So she pounced. She spent the summer researching water quality by treating water samples in a chemistry lab, and stayed on in the lab through high school and college. She loved the hard science - the microbiology and chemistry - but also the bigger picture. "You're connected to land, but you don't think of all the ramifications of pesticide use and fertilizer use," she said. "The broader environmental human health effects were pretty compelling."
That big picture aspect is important to many women, she's discovered. "I often see female students who say, 'I want to be in engineering to help people, to have positive impacts on society and the environment.'"
Women also lag behind in computer science. Only 19 percent of software developers are women, according to the Bureau of Labor Statistics. And this means women may be missing out on incredible job opportunities, said Maria Klawe, president of Harvey Mudd College.
"It's not just about going to work for a place like Google or Microsoft or Facebook," she told the NewsHour in an interview with Judy Woodruff that we'll post on the NewsHour website tomorrow. "It's about doing computer science and medicine, or computer science and arts, or computer science and languages, or doing educational software. ..The careers are out there, they pay really well, they're very flexible, and they're great opportunities to combine the career with family.
Plus, she adds, losing that female perspective translates to the technology we're not seeing in the market.
"If you cut out essentially half of the population, you're going to have a lot of creative ideas that never make their way into technology, because you're just not having those people involved in it."
A new paper looks at yet another area where women are lagging: patents. Only 5.5 percent of commercial patent-holders were women, according to the paper. And the gap can't only be attributed to fewer women in the field. Even within the field, female engineers are less likely than males to work in development or design, where patents originate, according to Jennifer Hunt of Rutgers, the paper's lead author.
And this has serious economic consequences: Eliminating the patenting shortfall "would increase U.S. GDP per capita by 2.7%," the paper says.
Retention is another important part of the puzzle. Hunt has also studied women who exit the science and engineering fields. In most fields of science, she found, the exit rate for female engineers is much higher than in other scientific fields. And the more male the field, the more women are likely to leave, her data shows. She also found their reasons for leaving often linked to pay and promotion.
"Women in the engineering field are having a harder time advancing compared to other fields," she said.
A lack of female mentors, subtle discrimination or work conditions in which men talk in a way that women found disrespectful were also common factors. "That sort of thing can be offputting and harder to measure, Hunt said.
Madline Heilman, a psychology professor at New York University and an expert in gender stereotypes, thinks the problem is more deeply rooted than many realize. Women, Heilman said, are seen as communal, caring, emotional and concerned about others; men as intellectual, rational, logical.