Amid rising instances of field enumerators coming under attack across at least three states for some of the ongoing NSS surveys and gathering mistrust over CAA and NRC, the house-listing operation and the updation of the National Population Register, set to begin in April for Census 2021, could run into rough weather. The survey system is already in "deep trouble" and given the increasing instances of such attacks, conducting household surveys with the Census as the frame would be "very tough" going ahead, Pronab Sen, former Chief Statistician of India and Country Director for the India Programme of the International Growth Centre, said. Amid the backdrop of protests and rallies on the new citizenship law, the National Sample Survey Office field officials have been attacked in some areas of Kerala, Uttar Pradesh, Andhra Pradesh and West Bengal. Sen said that this could have an effect not just on the Census but on other surveys as well. On this edition of the Big Picture we will analyse the importance of census and the challenges in gathering data.