"In her paper, published in the Journal of Sex Research this past June, Balzarini compared the demographic backgrounds of 2,428 polyamorous individuals and 539 monogamous ones by asking participants to take an online survey. Her team found that polyamorous people tend to identify more as bisexual/pansexual, are more likely to report being divorced, and make less money yearly than monogamous couples."
"When it came to monogamous relationships, 74 percent of straight respondents reported being monogamous compared to only 17 percent of bi/pan respondents. (The remaining percentage identified as gay/lesbian or other.)"
Also, this is entirely anecdotal, but in the various circles I'm a part of, every single polyamorous person I know is queer to some degree. Granted, a lot of that is because the people in my circles are disproportionately queer, but not nearly so much that it would be the sole reason for that.