Hmmm, we started in a monogamous relationship. Over 20 years worth of one. For us, Gator (the man) had a wife (Vol-me) that was willing to consider a poly relationship.
Now, I belong to a poly forum and see the situation arise both ways. And since I've never been in your shoes, I can't say that it has occurred to me to actually notice if it is more prevalent for woman to have partners more open to a non monogamous relationship. I hope that if it were something easy to spot, Id have picked up on that by now.
Vol