i. Primary sources of the demographic data are the census, the surveys, the registrations, migration reports, estimates and projections of which the census continues to be the most important single source of basic data for population geographers.
ii. Egypt, Babylonia, China, Rome and Palestine were the countries where the census was begun during ancient times.
iii. The first census is believed to have been done to count the number of able-bodied men who could be used for war.
iv. The modern census is defined as the process of collecting, compiling and publishing demographic, economic, and social data pertaining to a specific time, to all persons in a country or delimited territory.
v. The modern census has many features-
(a) Each individual is separately but only once enumerated,
(b) Takes place in a precisely defined territory,
(c) It covers majority of population,
(d) Is taken at regular intervals,
(e) Should be completed within a given period of time and
(f) Should be published after due verification.
In Europe, Sweden's census of 1749 is sometimes regarded as the first but the first complete census of population was conducted in 1881 on a uniform basis throughout India.
Indian census is recognised as one among the well thought and well-planned census of the world.
The general problems associated with census include-the use of terms, shortage of trained personnel, extremely tedious fieldwork people do not give correct information and there are wide gaps left while finalising performas.