Anyone with enough wealth can buy into it just as the current execs have.
And to address your post below... Here are a few female Fortune 500 execs.
Claire Babrowski RadioShack
Brenda C. Barnes Sara Lee
Dorrit J. Bern Charming Shoppes
Mary E. Burton Zale
Patricia Gallup PC Connection
Susan M. Ivey Reynolds American
Andrea Jung Avon Products
Kay Krill AnnTaylor Stores
Linda A. Lang Jack in the Box
Kathleen A. Ligocki Tower Automotive
Anne Mulcahy Xerox
Janet L. Robinson New York Times
Paula G. Rosput Reynolds Safeco
Patricia F. Russo Lucent Technologies
Mary F. Sammons Rite Aid
Marion O. Sandler Golden West Financial
Stephanie A. Streeter Banta
Margaret C. Whitman eBay
Mary Agnes Wilderotter Citizens Communications
Taken from 2006.
There are also what... 5 Black F500 CEOs? 13 or 14 others by people of non-white decent?
Basically what it boils down to, is money. Find a way to get it, and you win!
Couple reasons could be cited. One of the major reasons is they have to make up for the lost time that females tend to bring to the job.
Women 'take 46 per cent more sick days than men' | Mail Online
Women Take Almost 50 Percent More Short-term Sick Leave Than Men
That's not counting pregnancy and maternity leave. In which during the pregnancy part women are more likely to be doing less of their job duties, have ill tempers regarding any "possible" hostility, and often require other special accomodations.
Just to be clear though, do you think you could find a job with the same exact duties in which a female makes less than a man per hour? Because from what I understand it's that females often make less per year than men in the same or different jobs... and that boils down to the days taken off work (see above) and overtime taken.
In this country, anyone can be anything as long as they are able to work themselves to death to get there.
Of course it helps if you've got the means to afford the education that you want first... but if not, you can still get there on your own.