My, how times have changed: A woman, Hillary Clinton, is a serious contender to be the next US president. But maybe they haven't changed all that much: According to the US National Center for Women & Information Technology (NCWIT), there has been an astounding 70 per cent decline in the number of incoming undergraduate women choosing to major in computer science between 2000 and 2005.

These numbers indicate a dramatic shift downward in women in high tech, but they don't tell us why. It could be that employment opportunities in high tech haven't gotten better for women since the 1980s, when females first started to break into the technology field. Or perhaps something deeper is going on: Perhaps women have decided that high tech is not a career path worth pursuing and are looking elsewhere.

Despite major efforts by the US National Science Foundation, IEEE, ACM, and others in the 1980s to encourage more women to enter the computer science and engineering professions, the latest numbers gathered by NCWIT show little progress. Although women hold 51 per cent of professional positions in the United States, they hold only 26 per cent in IT and just 13 per cent of C-level positions in Fortune 500 technology companies. Statistics from the US government show a similar pattern.

And there's not much hope for a new wave of women to step into these positions. Although girls took 56 per cent of all Advanced Placement (AP) tests in high schools -- the tests typically targeted by university-bound youths -- only 15 per cent of AP computer science test-takers were girls.

Research by Stanford University professor Shelley Correll indicates psychological pressure keeps many women from pursuing such careers, especially at the executive level. Her research indicates that women are often aware of the stereotypes about their gender, which causes them to judge their own abilities by unreasonably high standards, in order to prove the stereotypes untrue. That leads some women to pull back from leadership positions when their instincts clash with those stereotypes.

Five who've succeeded in the boys' club

Surveys tell you the pattern, but they don't provide the insight, much less the road map. So we interviewed five women who have attained lofty positions in high tech to uncover what propelled them into the field and what has kept them successful in the IT boys' club over the years.

Tamara Casey, CEO of 4DK, is probably best known for her 14 years as vice president of technology strategy, architecture, and research at Nextel Communications. Today she is CEO and co-founder of 4DK, a company whose middleware appliance connects communications networks.

Susan Major is the managing partner for the Global Technology Practice at DavenportMajor, an executive search firm. Earlier in her career, as an executive at Motorola, she introduced two-way radios, cellular handsets, and the first Motorola PDA.

Beatriz Infante is the CEO of VoiceObjects, a provider of adaptive self-service phones. She has also been CEO of Aspect Communications and senior vice president of Oracle's Application Server division.

Lucy Sanders is the CEO and co-founder of NCWIT and is executive-in-residence for the Atlas Institute, a think tank for communications and computer technology at the University of Colorado in the US. She has also been an executive AT&T Bell Labs, Lucent Bell Labs, and Avaya Labs, specializing in systems-level software and solutions.

Claudine Simson is CTO of semiconductor maker LSI Logic, and previously was CTO at Motorola.