National Demographic Survey 1968
Population growth has been rising rapidly in the Philippines in the sixties. Although population censuses can measure this rapid increase, it was realized that censuses are only held once every ten years and that population size is affected by other forces in the environment which are not covered by the census. Thus, the decision to conduct the first National Demographic Survey (NDS) jointly undertaken by the University of the Philippines Population Institute (UPPI) and the then Bureau of the Census and Statistics (BCS), now known as the National Statistics Office. This survey, though covering only a fraction of the population, focused on the fertility aspects of the ever married woman. It was also designed to estimate the rate of population growth; to measure the pattern of mobility (both spatial and occupational) and educational attainment; and, to determine the interrelationship between these variables.
The survey was conducted during the period May-June 1968. Being a nationwide survey, a stratified 2-stage sampling method was used for both the rural and urban areas using the 1960 census as the frame yielding a 7,256 representative sample of all households in the country (completion rate: 98.6%). Urban-located households were drawn randomly from previously random selected precincts, to which the former were registered for election purposes. On the other hand, rural-located households were drawn randomly from previously random selected barrios. To adjust any differences between the urban and rural samples, a weighting scheme was imposed.
The survey, being a BCS-UPPI joint project, made use of a BCS formatted questionnaire which UPPI extended to include questions on fertility, mobility and labor force. All ever married women in the chosen households, aged 10 years and above, were personally interviewed by either male or female interviewers, who in turn were trained on how to translate the questions from English to the appropriate vernacular.