Take a look at the senior management of Apple. Every senior executive is male. At IBM, it's 10 of 12. And at Texas Instruments, it's 3 of 12.

Then consider how many technology companies have a female CEO. Since 2009, there had been Yahoo until Carol Bartz was ousted this week. Xerox. Hon Hai Precision Industries, Apple's biggest contract manufacturer. There's Advent Software, founded by Stephanie DiMarco in 1983. Then it gets more difficult.

Of course, there are a number of top women executives slightly below the CEO level.

Safra Catz has been one of Oracle's presidents since 2004 and started her second stint as CFO this year. Sheryl Sandberg is COO of Facebook after being a VP at Google. Linda Sanford is a Senior VP at IBM for enterprise computing. Weili Dai is co-founder and VP of Marvell Technology Group.

But why so few at the top? Given that young women now outnumber men in graduate schools, there ought to be more. Surely, as far as consumption of technology products goes, from iPhones to Kindles, they are a huge market.

Other women have led technology companies with mixed results. Carly Fiorina was lured away from Lucent Technologies to HP and was fired as CEO. Patricia Russo was a CEO of Lucent until its takeover by France's Alcatel but left because there was no need for two bosses. Meg Whitman was CEO of eBay for 10 years until she decided to run for Governor of California.

Now, both Russo and Whitman are HP directors.

Will there be change over the next decade? Signals are mixed. But women were 50.8 percent of the U.S. population, the 2010 census reported.

Girls are nearly 50 percent of high school students who take the Advanced Placement exam in calculus but only 19 percent of the AP computer science test takers, the College Board reports.

In college, something happens. By graduation, women received only 18 percent of degrees in computing and information sciences in 2009, a sharp decrease from the 37 percent in 1985, according to the National Center for Women & Information Technology.

There are similar disparities in electrical engineering, the traditional source for semiconductor and computer industry talent. Both Bill Hewlett and David Packard were electrical engineers.

Of the 407,000 members of the Institute of Electrical and Electronic Engineers (IEEE), 90 percent were male in 2010, despite years of supporting technical education for women.

Statistics also show that women engineers and technologists often leave the workforce in mid-career because they want to raise children or spend time at home. But other figures show they leave the technology sector for another. So that by the time comes for promotions, there are fewer women to choose from.

In Silicon Valley, there are many women just below the CEO's level, like HP's Ann Livermore, an Executive VP. Livermore was twice passed over for HP CEO and now, at least is a director.

One reason why Ursula Burns was elected Xerox CEO in 2009 was that then-CEO Ann Mulcahy was afraid to lose her to another company.

Livermore has an MBA; Burns is a mechanical engineer. The Xerox CEO declined to comment on Bartz's Yahoo ouster, her spokesman said to IBTimes.

Then there are several stars who have either been serial successes or persistent innovators. Judith Estrin, an E.E., co-founded Bridge Networks, which helped form 3Com, then co-founded Packet Design which was bought by Cisco Systems, which made her Chief Technology Officer. Now she runs JLABS, another networking company.

Bartz, now ex-CEO at Yahoo, was recruited there in part because of shareholder agitation by investor Carl Icahn. Bartz is a computer scientist. After a high-paced rise at Sun Microsystems, she was recruited as CEO of Autodesk, the design-software developer. After 12 years, she stepped aside in 2006 because she didn't want to lose her male COO, to another company, she said in an interview.

As she disclosed this week, Bartz was fired in a telephone call by her chairman, director Roy Bostock, after a board decision. Yahoo has two women directors; nine others are men.

In a parting e-mail, the 63-year-old executive noted: I've just been fired over the phone by Yahoo's Chairman of the Board. It has been my pleasure to work with all of you and I wish you only the best going forward.

Yahoo didn't announce any reason for the firing. But the board could not necessarily be faulted. On the day Bartz took over, Yahoo shares closed at $12.09. On the day she was fired they were at $12.91.

Sandra Kurtzig, who founded ASK Group in 1972, is a mechanical engineer who built that company into one of Silicon Valley's biggest mid-range computer software developers. She sold ASK to CA Technologies in 1994. This year, she started Kenandy, another software developer, with $10.5 million from Kleiner Perkins Caufield Byers, Salesforce.com and the Wilson Sonsini law firm.

There are also several younger CEOs, like Kim Polese, a former Sun Microsystems Java developer, who founded Marimba, a software developer acquired by BMC Software. Polese started another company, SpikeSource, which was bought by Black Duck Software.

Right now, Polese, 39, a biophysicist, is serving as a fellow at Carnegie Mellon University, but probably will start another company before long.

Another executive is Diane Greene, 57, a mechanical engineer who co-founded VMware, the virtualization software specialist, and was CEO until 2008. Greene and her spouse, a computer scientist, got a large part of the $625 million EMC paid for VMware in 2004 and then profited when VMware went public, so chances are she will be heard from again.

Marvell's Dai, 49, is a computer scientist who co-founded Marvell, the chip designer, and has been COO of its communications business group. Her spouse is co-founder and CEO of the Bermuda-based company.

To inspire and recruit women to engineering and technology, it's probably a good thing that several of the best U.S. research universities have women presidents with science backgrounds.

Princeton has Shirley Tilghman, a molecular biologist who is also a director of Google; Massachusetts Institute of Technology has Susan Hockfield, a neuroscientist who is a director of General Electric. Rensselaer Polytechnic Institute has Shirley Ann Jackson, a physicist, who is a director of IBM and Medtronic, among others.

These academics can encourage women students as well as agitate for more women in top management. Clearly, Jackson has plenty of work to do at IBM. As does Tilghman at Google. And Hockfield at GE where one of her co-directors is Avon Products CEO Andrea Jung, an Apple director.

At Apple, Jung is the only female director. There's a place to start.