Katharine Graham was the first woman elected to the Associated Press's board of directors. She's seen here with the board in New York in 1975. (AP)

The number of S&P 500 companies with all-male boards of directors has now dropped to an even dozen.

A decade ago, 60 companies — that's 12 percent of the S&P 500 — didn't have any female directors on their boards. Even 10 months ago, the research firm Catalyst listed 18 companies without a single woman. Yet the pace of change has quickly accelerated and the number has today plummeted to only 12 companies, or about 2 percent.

In other words, it appears corporate leaders are getting the hint. Not only do they seem to have accepted the idea, backed by study after study, that more diverse boards make good business sense. They also seem to have recognized that an all-male board in 2015 is simply no longer worth the headline risk.

To see which holdouts remain, we asked S&P Capital IQ to search its database for how many companies in the S&P 500 still don't have any female directors in these key roles. It turned up the following 12 companies, which mostly hail from male-dominated industries like energy, technology and automotive. Here's the list:

1. Cabot Oil & Gas
2. Cimarex Energy
3. Delphi Automotive
4. Diamond Offshore Drilling
5. Discovery Communications
6. Equinix
7. Garmin
8. Joy Global
9. Linear Technology
10. Precision Castparts
11. Qorvo
12. Wynn Resorts
Source: S&P Capital IQ

At least two of these come with an asterisk, though, as they've either had — or nearly had — a woman on their boards. The first is manufacturing company Precision Castparts, which recently nominated Gen. Janet Wolfenbarger, a retired commander of the U.S. Air Force, to be voted on as a director at its annual meeting. But with the company's announcement Monday that it will be acquired by Berkshire Hathaway, Gen. Wolfenbarger and the other new nominees will no longer stand for election.

The second company, Las Vegas casino conglomerate Wynn Resorts, had a woman on its board until recently. After a heated proxy battle, Elaine Wynn, the ex-wife of company CEO Steve Wynn, lost her seat. That has now left the board with no women, a fact she pointed out as part of her campaign to remain on the board.

In an emailed statement, a spokesman for the company said the board is "dedicated to having a board that represents a diversity of backgrounds and perspectives" and is committed to growing its board by one additional female or minority candidate by year's end.

Internet services company Equinix made a similar case, noting the company currently has an open board seat and that diversity will be a key consideration in filling it. "We are in the midst of an extremely competitive global talent market," its chief of human resources, Debra McCowan, said in an emailed statement.

The other companies declined to comment or did not return a request to do so.

Of course, once these companies actually get to even a single female director, that doesn't necessarily mean a better board dynamic will immediately follow. Research has shown that it is not until women reach critical mass, or the point when there are at least three female directors, that they're able to create real change.

That's still a ways off for most companies. While almost every board in the S&P 500 now has at least one woman, far fewer have a critical mass. The overall percentage of women who sit in these powerful corporate director seats has moved at a glacial pace over the years, ticking up from 15 percent of all board seats at S&P 500 companies a decade ago to 19 percent last year.

Just ask Liz Dolan, the lone female Quiksilver director who recently resigned from that company's board. Writing in Fortune, she described publicly how she believes things would have gone better had she not been the only woman in the room. "What I learned is that even when a woman earns a seat at the table," she wrote, "the men can put you in a soundproof booth."

Read also:
Women still hold only 19 percent of U.S. board seats

Nearly 30% of new board members appointed this past year were women

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