The National Sample Survey was initiated by the government of India in 1950 to collect socioeconomic data for the entire country on a sampling basis. The April-June 1951 sampling included a small section for fertility data, to make up for the lack of a total vital registration system in the country. By the 7th round in October 1953-March 1954, birth, death, marriage, and morbidity data were included in the survey. The sampling design involved a multistage, stratified data collection system with interpenetrating subsamples, and used households as the unit of measure. By the survey of 1958-1959, the collection of demographic data was being accorded a high priority. The interpretation, i.e., adjustment, of the collected data is discussed and illustrated with tabulated data. - See more at: http://www.popline.org/node/516932#sthash.Mwc1hlaO.dpuf