The Demographic Sample Survey is another method of data collection for population studies. In a sample survey, information is collected only from a sample of the population, which is representative of the whole and from which conclusions are drawn by the use of scientific methods.
In a country like Afghanistan, where no census was conducted, population data were collected through sample surveys and some estimates were made of its size, growth, structure and characteristics.
Even in countries where regular census operations are conducted, the need for collection of population data through sample surveys is felt, for a census is taken in most countries only once in ten years.
The collection of data through sample surveys has several advantages. In the first place, with the help of specially trained interviewers and carefully prepared questionnaires, some special aspects of the population can be studied in depth.
For instance, information on abortions, contraception, etc., so essential for the study of fertility, can never be obtained from a census, but only through special sample surveys.
The quality of data obtained through a sample survey is better than that obtained from a census because they are collected by a comparatively small number of well-trained interviewers.
Despite these advantages, however, sample surveys can never take the place either of a census or of vital registration.
A complete coverage of the entire country at a point of time and a continuous and current registering of vital events are unique features of the census and the vital registration system respectively.
Sample surveys, however, are becoming increasingly useful to planners and administrators in many ways. The methodology of conducting surveys has also improved over time.
Some Important Demographic Sample Surveys Conducted in India: By using the technique of the sample survey, several demographic surveys have been conducted in India.
The National Sample Surveys, Surveys conducted by the Institute of Politics and Economics, Poona (1952-1956), the Mysore Population Study (1953), the Patna Demographic Survey (1955), the Family Planning Survey conducted by the Operations Research Group (ORG) (1970) are some such important surveys. Information about two important surveys is presented in following paragraphs.