Twitter, unlike Facebook, never asks users to share their gender. Yet its recently-public Analytics tool can tell you, among other demographics, the male-female ratio of your followers. That’s because Twitter relies on the magic of algorithms to designate—and perhaps reassign—user gender.

See also: Twitter Unveils A New Time-Waster: Tracking Your Popularity

Now, Twitter is abuzz with how predominantly male their followers seem to be. Just search “Twitter gender” or “Male followers” to see hundreds of surprised tweets about how inaccurate Twitter’s gender-identifying algorithm seems to be.

Glenn Fleishman notes on Boing Boing that even a friend of his whose bio reads “Feminist killjoy” had a 75% male following. His curiosity led him to a 2012 post on Twitter’s advertising blog, which indicates a 90% accuracy rate for targeting Twitter users’ gender:

“Similar to our approach to interest targeting, we’re able to understand gender by taking public signals users offer on Twitter, such as user profile names or the accounts she or he follows. We have strong confidence in this approach. A panel of human testers has found our predictions are more than 90 percent accurate for our global audience.”

In other words, gender on Twitter is determined by behaviors and interests. Though I usually speak to other women on Twitter, my follower ratio is said to be 77% male, though this is probably because my followers are interested in technology, and Twitter is presumably assigning that as a male interest.

My tweets, which are heavy on technology, lead to me getting targeted with advertisements for tech services. But if Twitter ever catches on that I’m a woman, here’s how my experience could change:

Twitter hasn’t responded to ReadWrite’s request for more information on how it determines and assigns gender to users.

There’s no way to opt out of gender assignment on Twitter, perhaps for the same reason there’s no way to opt in. Fortunately, since Twitter’s gender assignment seems largely based on the interests you’re tweeting about, it shouldn’t be too noticeable. It’s just another less-than-politically-correct shortcut to targeted advertising.