A simple two-stage data collection procedure to handle unit non-response in social surveys

The aim of this paper is to investigate the possibility of collecting information on the reproductive behaviour of mothers by means of a two-stages data collection procedure. At first stage a simple self-filled questionnaire is administered to a sample of students attending compulsory school; thus, each pupil is asked to give his mother a more complex questionnaire, bringing it back to school. Linking the two questionnaires, the non-response selection problems are solved using the same statistical techniques used to control attrition in panel surveys. Even if self-filled questionnaires can not be too complex, in some cases this data collection procedure can be recommended as (1) the proportion of unit non-responses in standard surveys can be very high, and the unit non-response selection is not easy to control; (2) it is a very low cost data collection procedure. After a general description of this data collection technique, an application is performed using data of the Urban Fertility Survey (UFS) conducted during 2001-02 in four Italian towns. As respondents are clearly selected (e.g., by citizenship) if data analysis is performed without correcting for non-response, results may be biased. In particular, we compare some regression models explaining fertility using data collected by the two questionnaires.