A recent editorial in Neuropsychopharmacology by Chloe J. Jordan and the Editor in Chief, William A. Carlezon Jr. overviews the participation of scientists in the journals' workings by gender. I was struck by Figure 5 because it is a call for immediate and simple action by all of you who are corresponding authors, and indeed any authors.
The upper two pie charts show that between 25% and 34% of the potential reviewer suggestions in the first half of 2018 were women. Interestingly, the suggestions for manuscripts from corresponding authors who are themselves women were only slightly more gender balanced than were the suggestions for manuscripts with male corresponding authors.
I have for several years now tried to remember to suggest equal numbers of male and female reviewers as a default and occasionally (gasp) can suggest more women than men. So just do it. Commit yourself to suggest at least as many female reviewers as you do male ones for each and every one of your manuscripts. Even if you have to pick a postdoc in a given lab.
I don't know what to say about the lower pie charts. It says that women corresponding authors nominate female peers to exclude at twice the rate of male corresponding authors. It could be a positive in the sense that women are more likely to think of other women as peers, or potential reviewers of their papers. They would therefore perhaps suggest more female exclusions compared with a male author that doesn't bring as many women to mind as relevant peers.
That's about the most positive spin I can think of for that so I'm going with it.