(a) De facto methods: A de facto census is one that counts all persons as residents of the place they happen to be at the time the census is taken. In practice, de facto censuses are conducted in such a way that most people are counted in the places they usually live, but not always.
Advantage: Very clear and simple, international comparison are easy, the time taken is short and the information obtained is reliable.
Disadvantage: Floating population not counted, large number of trained and qualified personnel is required and mistakes occur because of rapid and fast method o f enumeration.
(b) De jure methods: When a de jure census is taken, there is always some uncertainty abut what should be considered a person's usual or normal place of residence.
College students, for example, often live for 9 or 10 months in a year in the community where they attend college.
Yet during summer months and holiday periods, they may live in the homes of their parents, which may be in different communities or states. Which is their usual place of residence?
Advantage: Due to availability of sufficient time, inaccuracies are reduced to the minimum, more questions can be asked, and the information obtained is dependable.
Disadvantage: Difficulty arises in the definition of temporary, and permanent, birth and death goes uncounted between the periods and it is difficult to count persons who have no permanent address.