Instead of going through all this trouble trying to figure out whether you are male or female, you'd think Twitter would just use a checkbox for gender in account settings.
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. And where we can't predict gender reliably, we don't –– and those users won't be targetable through this feature.