Okay, so now your signup form has "first name", "last name" , plus "preferred name". Seems pretty minor, doesn't it, yet adding that next question drops signups

Okay, so now your signup form has "first name", "last name" , plus "preferred name". Seems pretty minor, doesn't it, yet adding that next question drops signups say 4%. Is it really worth asking the question if you're going to scare away 4% of your customers? Or do you try to make due with what you have?