There is a marketplace where corporate boards of directors demand board members, both male and female. That marketplace also has a pool of candidate resources which we could call the supply of board members, both men and women.

Directors are selected, in part, from members of top management, specifically the 5 highest paid positions in major corporateions. Currently, women constitute somwhere around 6% to 8% of that top tier of management among the S&P 200 firms.

Corporate boards have managed to select women directors at over twice that rate: more like 16% of the independent director seats on boards at S&P 200 top tier firms, according to Spencer Stuart's Board Diversity Report for 2009. A significant majority of boards surveyed have stated that they are "looking for women and other diversity candidates."

In basic economics, the supply-demand curves describe these two profiles. At their intersection, an equilibrium market price and quantity are said to result.

Boards of director have increased their demand for women (and diversity candidates) by reaching beyond corporate management ranks and conducting searches among academia, entrepreneurial firms, and consulting firms (finding law, accounting, and investment partners).

Under normal market circumstances, assuming an upward-tending supply curve, as boards pursue more women candidates, the demand curve would move outward from D1 to D2. The quantity of women tapped for boards would increase from Q1 to Q2, and the price would increase from P1 to P2.

This was the case in Norway when the country mandated a 40% quota for either gender on the boards at state organizations and ultimately public company boards of directors. The demand curve was pushed out, and women became a highly valued commodity.

If the supply of compentent and experienced women capable of taking on top corporate board roles is limited, then the supply curve is not normal. Instead, it looks more like a stick figure. Supply is constrained, such that no matter how much demand and price are increased, little or no increase in the actual quantity results.

The supply curve describing the availability of women candidates for corporate directors is constrained: it is steep and inflexible, such that increases in director compensation in the post-Sarbanes-Oxley environment in the US have resulted in only small increases in the number of qualified women available to serve on public company boards.

Only the larger increases in compensation from P1 to P2 have resulted, with only small increases (if at all) in the quantity of female candidates from Q1 to Q2.

• some companies delisted rather than comply; others went private, were acquire or merged, reducing the demand for directors rather than increasing it;
• companies reached into the upper management ranks and tapped women who were not quite ready, either in terms of age or experience; companies lost that executive talent before it could be fully developed experientially; boards ended up with directors not quite ready to perform at peak levels in public company governance; companies saw shortages of talented women in their top ranks;
• some companies reached into the European market to find experience women for their boards, infusing Norwegian companies with non-Norwegian governance experience (for better or worse);
• a few top women directors doubled and tripled their board service: 70 select women reportedly now serve on over 300 boards;

Many women on board advocates "pooh-pooh" the idea that the supply of qualified women director candidates is constrained. The evidence suggests otherwise. Women continue to over-board themselves at non-profits; they do not form boards of directors for their own entrepreneurial firms; many "opt out" of corporate leadership; women network among themselves rather than mixed-gender professional associations; and finally, when women attend panels on corporate governance, they ask almost "naive" questions which reveal that they have not yet acquired the appropriate relevant experience or training.