@Shak
In a number of countries,the census is conducted through forms that are sent to each household by post. You fill the form and send it back by post or it is collected by a government's agent. This obviously requires everyone to have post office addresses etc. It also presumes a high level of literacy. Soon some countries will be able to do it thro the internet. We are still a long way from there so ours will have to be done door to door by enumerators for a long time to come.
One example - the UK -
http://www.ons.gov.uk/ce...lect-process/index.html
'The last census was carried out in 2001. A census form was delivered to every household,establishment,or to people living anywhere else,by a field force set up throughout the country.
The forms were designed for self-completion by form-fillers and to provide information relating to census day - 29 April 2001. Most forms were then posted back to temporary local offices and the remainder collected by the field force.
Everyone in the country was under an obligation to complete a census form,and a limited number of people were prosecuted for failing to comply with this obligation. A major publicity campaign helped raise awareness of the census and its importance. There was also a special programme to help various groups who might have difficulty with the census.'