This story is part of Solving for XX, a CNET special report exploring what people and companies are doing to make the tech industry more diverse, more equitable and more welcoming to women.
There's something about the number 30.
It's the age Silicon Valley considers workers over the hill.
It's how old Facebook CEO Mark Zuckerberg is now.
And it's the average percentage of women working in the tech industry, based on diversity reports published by 11 of the world's largest tech companies last year. In comparison, women make up 59 percent of the US labor force and almost 51 percent of the US population, according to the US Census Bureau.
Is 30 percent really so bad?
It is when you drill into the percentage of women filling leadership and technical roles -- that's when the numbers get downright depressing.
Consider Microsoft: In October, the company reported that women comprise 29.1 percent of its workforce, but only 16.6 percent work in technical positions and just 23 percent hold leadership roles. Twitter said women fill 10 percent of its technical jobs, with 21 percent in leadership. And women Googlers account for 17 percent of the search giant's tech jobs, while only 21 percent manage others.
These figures matter. For starters, they show few women influencing product development or business strategy -- the two rungs at the top of the industry's corporate ladder. That's not just harmful to women; it's bad for business. Studies show that companies with different points of view, market insights and approaches to problem solving have higher sales, more customers and larger market share than their less-diverse rivals.
So what's behind that 30 percent number at tech companies? It could be basic human nature, says Virginia Clarke, a recruiter for executive search firm Knightsbridge: diverse enough to show effort, while still surrounding ourselves with people who think and act as we do.
"It's almost like water seeks its own level," says Clarke. "This is the level where the majority feels comfortable. I would say its unconscious."
Scott Page, a professor of complex systems, political science and economics at the University of Michigan, has another theory. At 30 percent, there's an extremely high chance you'll see at least one woman in every meeting. That might be enough to gloss over the lack of diversity. If people see at least one woman in each meeting, they're not seeing a problem.
"That's not cause for alarm," Page said.
But the problem becomes glaringly obvious in meetings made up completely of men -- a likelihood that increases as the percentage of women falls below 30 percent. Heck, the testosterone-heavy Marvel superhero film "The Avengers" includes just one female super heroine, "Black Widow."
"The first step is acknowledging that there is a problem," says Clarke. "The problem is that the culture is obviously consciously or unconsciously exclusive, and people are exhibiting chronic behaviors that keep women -- and likely people of color -- out or not moving up."
Awareness of the diversity problem has spurred some action. Microsoft has been working on the issue since October, when CEO Satya Nadella said women in the tech industry should trust in karma instead of making a case for a raise.
"It's not really about asking for the raise but knowing and having faith that the system will actually give you the right raises as you go along," Nadellaat the Grace Hopper Celebration of Women in Computing (of all places). The company now provides training on unconscious biases that can prevent men from seeing their female colleagues' contributions.
Intel has, including tying managers' compensation to their progress in that area. Apple is donating $50 million to the Thurgood Marshall College Fund and the National Center for Women and Information Technology to help swell the pipeline of qualified women and minorities.
But the problems begin at an early age.
"Girls don't get as much opportunity to use computers," says Ariane Hegewisch, a study director for the Institute for Women's Policy Research. They also get fewer chances to explore subjects like mathematics or science, in part because of lack of encouragement, curricula that appeal more to boys than girls and a negative stereotype about girls' technical abilities.
Indiana University gets 8,000 freshmen every fall, about half of them women. Science and computing isn't on the radar for 97 percent of them, according to
Maureen Biggers, assistant dean for diversity and education at Indiana's School of Informatics. "It doesn't occur to them as a career path," she says.
While it's true the industry needs more women proficient in the hard sciences, success in the technology industry doesn't really require a technical degree. Oracle's co-CEO, Safra Catz, earned a law degree before becoming an investment banker. Hewlett-Packard CEO Meg Whitman has a degree in economics and an MBA. Facebook Chief Operating Officer Sheryl Sandberg also has a degree in economics and an MBA from Harvard Business School.
But few women with MBAs are likely to enter tech-intensive industries; and 53 percent of those who do, switch industries (compared with 31 percent for men), according to a study by Catalyst, a nonprofit organization focused on expanding opportunities for women.
The study also revealed that women in business roles within tech companies are more likely to start at the entry level compared with men. And when it comes to pay, women in Silicon Valley earn less than their male peers. In 2013, the median income for men with an undergraduate degree in Silicon Valley was 61 percent higher than for women, according to a February report by Joint Venture Silicon Valley.
"It may be that some of these professions have become more and more geeky and nerd-like," says Hegewisch. "Smart young women don't necessarily want to hang out in that culture and feel pushed out."
And that's the crux of the problem. Tech companies, no matter if they're industry heavyweights or fresh-faced startups, need to rethink how they assess job candidates, says Clarke, the executive recruiter from Knightsbridge.
"This comes down to a war for talent, and the best possible talent may not look like you," Clarke said.