Can anyone add some more data?

I have a theory. My theory is that lesbians are more likely to have lower singing voices than straight women. I don't have enough data to back this up, so I need more. Cross-referenced lists. Actual studies. Anecdotes. More anecdotes.

Here's where I'm getting my data from. Personally, I'm a solid tenor, which really freaks people out. Lucas Silveira is definitely an alto. So is Amanda Palmer. Kaia Wilson rarely strays above the mid-mezzo-soprano range at the highest. It's blashphemy, I know, but I don't own any of Melissa Etheridge or k.d. lang's music, so someone who does, please fill me in here. And I need even more data than this very short paragraph.

Of course, counterpoints to my theory are also welcome.