Census is such a huge exercise and a national census is not a joke and there are bound to be at least 1 or 2 % error , sometimes even more than that ,which simply cannot be helped...But it is also a fact that many minorities go unreported because of infiltration which does not happen with majority Hindus. We have had more than 400 infiltrators in our area most of them coming from Pakistan , if they can come all the way down here I am sure the numbers are far higher in the northern states ..They are sheltered by some relatives or friends and they become part of their community.But when it is a question of giving data for census they are unable to provide since there are many questions they need to answer like fathers name, mothers name and also siblings and then it is cross checked with the mosque authorities who normally have data for all the Musilm population that lives around there .. Normally the personcollecting data is supposed to report such matters and it is done.