Good questions, Amity. I don't have much time now to discuss it, but I'll try to highlight some of my thinking.
There are a number of times when it is expressly stated that when women are in the minority they speak less than their equal share of the time.
Women only spoke as often as their male counterparts when women held at least 60 percent of the board positions
When outnumbered, women used only 72 percent of their fair share of the speaking opportunities
The scholars previously documented the tendency for ordinary women to stay quiet when outnumbered, but Karpowitz was surprised to see it on school boards.
In majority-rule groups with few women, men were more likely to rudely interrupt their female peers.
Now, notice it doesn't say that women
never speak as much or more than their male counterparts, it is
only when they are outnumbered. Had it been the case that women never speak more than the men the authors would have said that in every case men speak as much or more than the women. Apparently when women comprise at least 60 percent of the board positions they speak at least as much as the men, otherwise the authors would claimed it was true 100 percent of the time. I believe it therefore follows that when women are in the majority they speak more than the men. Otherwise the authors would have said so, as they seem to be trying to make as strong a case as they can against men. I hope that makes sense to you.
As far as the article indicates the school board study was not presented in a respected, peer-review outlet. It is part of a chapter in a new book. Besides, I have little respect for peer-review. I've taken part in peer-review, and what it amounts to is that if you agree with the thesis of the authors you get a pass. If you disagree then the article doesn't get published. Editors select reviewers who agree with the editorial position of the magazine.
Clearly the authors are using highly subjective language and tests. Who determines what is a "rude" interruption? How can the authors objectively tell what the participants do or don't feel, as they pretend? Why do they think they can tell you what the motives are of men who interrupt? How do they know something was "hostile" or not?
A man is often the person in charge of a school board meeting. It is his job to interrupt or stop someone who is off topic. Why was this factor apparently not taken into consideration?
People tend to talk more on a subject they are familiar with and know something about. If men are in a majority they are going to talk about the school's football team or something else they know about. It has nothing to do with sexism or trying to dominate the discussion or not allow equal participation.
There are statistics like "On 10 of the 87 school boards, women spoke or made motions at less than half the rate of a board member’s equal share." Why are their no statistics about how often women dominated? This has every appearance of being cherry picked data.
A real study would not be taken from minutes of a school board meeting. I don't believe these are word for word transcripts; they are what someone decided was important to record. It could be that whoever made the minutes just decided that what the men said was more germane to the topic, or more important than what some of the women said. A real study would have all the data which others could look at and draw their own conclusions. A real study would have objective definitions and evaluations by those who did not have a stake in the outcome of the study.
The authors claim that “Women have something unique and important to add to the group, and that’s being lost at least under some circumstances." (from a link in this article). How can they know that something was lost? They don't know what was not said, so they don't know if it was important or not.
I'm out of time for now. See the excellent discussions pro and con that Mic0 referenced.