If you ask for demographics you will not only get increased abandonment, you will also get a lot of incorrect information, would it surprise you to know that I'm a 95 year old sumo wrestler? Your users don't care that you will get higher advertising rates due to "ad-target specific demographics". Don't ask for demographic information unless the user can see how it will benefit them directly. Facebook gets peoples correct birthdays (most of the time) because if you put in the right one, you get birthday wishes from your friends.
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If you ask for demographics you will not only get increased abandonment, you will also get a lot of incorrect information, would it surprise you to know that I'm a 95 year old sumo wrestler? Your users don't care that you will get higher advertising rates due to "ad-target specific demographics". Don't ask for demographic information unless the user can see how it will benefit them directly. Facebook gets peoples correct birthdays (most of the time) because if you put in the right one, you get birthday wishes from your friends.