The demographics pane displays stats based on sex, age and interests. How did it learn this private information?
How does Google Analytics know the sex, age, interests of visitors?
google analytics
Google can determine user's gender and age when an user provide his name to a google account or to a google partner. Having an user name is easy to discover the gender using a service like Dots Name Validation (http://www.serviceobjects.com/products/demographics-more/name-validation).Also many visitors uses a google account where their provide informations like gender and date of birth.As you may see, the information is not 100% accurate. It's just a small estimative.