“This is a national crisis,” says Nancy Ramsey. Ramsey, a futurist and co-author of “The Futures of Women: Scenarios for the 21st Century,” is talking about the state of women in computer science. She sounds appalled. She has every right to be.

In 2005, Ramsey, along with a fellow researcher, released a report for the Anita Borg Institute for Women and Technology that looked into gender imbalances in information technology. Six years later, she says, not much has changed, and the lack of women in the field is not only limiting the country’s creative and entrepreneurial output, it’s undermining the strength of our economy, and, by extension, our national security.

The gender disparities in the United States’ STEM (science, technology, engineering and mathematics) workforce are troubling. According to a report released last month by the Department of Commerce, although females fill almost half of the jobs in the American economy, less than 25 percent of jobs in STEM fields are held by women. Even worse, female representation in the computer science and math sector — the largest of the four STEM components — has declined over the years, from 30 percent in 2000 to 27 in 2009.

Americans — and their elected officials — should take note. According to the U.S. Bureau of Labor Statistics, the employment of computer scientists is expected to grow a whopping 24 percent between 2008 and 2018, which the Bureau says is “much faster” than average for most occupations. Rebecca Blank, acting secretary at the Commerce Department, tells me that because of this increased need, the participation of more women will keep the industry, and the country, globally competitive in the long run.

These realities have significant implications for the economy on a more micro level: Women in traditionally well-paying STEM jobs, particularly computer science, enjoy more wage parity with men than in other occupations. Lack of female presence also has long-reaching cultural and social ramifications. Christianne Corbett, a senior researcher for the American Association of University Women and co-author of the 2010 report “Why So Few?,” is blunt: “The growth of technology is driven by the people who are designing it. Without women at the design table, the interests of half the population will basically be ignored.” Adds Lucy Sanders, CEO of the National Center for Women and Information Technology: “We don’t know what women would invent because by and large right now, they are not.”

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It starts young. Although girls have achieved meaningful parity with boys in test scores and college degrees in math and science, they are also being sent a message that embracing these subjects is anathema to what it means to be female. (Mainstream Hollywood movies about technology innovation that relegate females to sexualized-accessory status don’t help matters. Neither do sexist comments from Ivy League university presidents or pink T-shirts for ’tweens with phrases such as “Allergic to Algebra.”)

“We are back to the beauty versus brains saga, in which girls entering middle school feel forced to ask themselves, ‘Do I want to be smart in math, or do I want to be seen as attractive?’ ” says Jennifer Skaggs, a University of Kentucky education researcher and author of the June 2011 paper Making the Blind to See: Balancing STEM Identity With Gender Identity. “If a female is seen as technically competent, she is assumed to be socially incompetent. And it works the other way around.”

Maresa Leto, 19, a sophomore at Michigan State taking her first computer science course this semester, understands this well. “I think it’s just part of what teenage girls are taught, which is to act dumb and cutesy so they don’t intimidate guys,” says Leto, whose older sister Lauren, a tech entrepreneur, urged her to give programming a try. As for the computer science class she’s taking, Leto says that she is one of a handful of women in the class. “No one has commented on the gender disparity, but I am conscious of it. I try to seem smarter than I actually am, just to prove I belong there.”

Cultural expectations of femininity and peer pressures are enormous influences — and problems — but they can be overcome by even the seemingly smallest of attitude adjustments. Lenore Blum, a prominent professor of computer science at Carnegie Mellon, has studied gender breakdowns in the technology industry both here and abroad and says that in countries such as Malaysia and Qatar, one of the biggest factors contributing to higher percentages of women in tech is the microculture they inhabit.

She points to a study done in Israel and published in 2006 in which researcher Orit Hazzan compared female students taking AP-level computer science courses at Hebrew-speaking and Arabic-speaking schools. The percentage of girls taking the courses in the Hebrew-speaking schools was at about 28 percent, five percentage points higher than that of a suburban U.S. public school at the time. (Females currently make up 19 percent of American AP computer science test takers.) The Arabic-speaking schools, however, had 61 percent female involvement. “In the Jewish community, the peer pressure [against girls in tech] was stronger than the influence coming from parents and teachers,” she says. “In the Arab community, the parents and teachers were the biggest influences. They saw proficiency in technology as a way for their girls to achieve upward mobility.”

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If, and when, young women do get into the technology workforce, the pressures don’t exactly let up. Although none of the female engineers I spoke with described explicitly hostile treatment while working in and around tech, many did acknowledge being acutely conscious of the low numbers of women — and, by extension, female mentors — around them. (Telle Whitney, president of the Anita Borg Institute, says that although about 21 percent of entry-level computer engineers are female, by the time you get to the top level, that number declines to 5.)

Media representations don’t help, either. On Friday, the Geena Davis Institute on Gender in Media will release a study on occupational representations and gender in G-rated films. The study, titled “Occupational Aspirations: What Are G-Rated Films Teaching Children About the World of Work?,” reports that between 2006 and 2009, there were no depictions of female characters involved in any sort of STEM career in children’s movies. And despite efforts on the part of tech magazines to showcase more female tech talent, it’s a lot more common to see stories such as this month’s “Bubble Boys” feature in New York Magazine showcasing no fewer than four young Silicon Valley computer programmers, all of them male. “That article was written through a narrow lens that took more than one cue from ‘The Social Network,’ ” griped one woman on an e-mail group list I belong to. “When will folks get tired of the computer engineers boys’ club?” asked another.

There are some indications that perhaps they already are. Blum tells me that Carnegie Mellon’s freshman class of computer science majors this year is 32 percent female, a jump of six percentage points from last year’s. (Stanford University’s numbers are lower but show a slight increase: 18 percent from 2009 to 2010 and a projected 20 percent for 2010 to 2011.) “Around a third is when you have critical mass — it changes the atmosphere in everything,” she says. “I don’t want it viewed as an aspiration— it’s not 50 percent. But it starts to be enough that you don’t have the phenomena of being a minority.”