There are four types of questionnaires in the SHP: a household grid questionnaire to assess household composition, a household questionnaire, an individual questionnaire and a proxy questionnaire. All household members aged 14 or older are eligible to answer the individual questionnaire. Each household has a reference person who completes the household grid and the household questionnaire. The household reference person also completes the proxy questionnaire to gather information on household members younger than 14 years, those who are absent for the time of the fieldwork, or who are unable to respond themselves due to illness or disability.
At present, the SHP comprises four samples: the SHP_I (5,074 households and 7,799 individuals interviewed first in 1999), the SHP_II (2,538 households and 3,654 individuals interviewed first in 2004), the SHP_III (3,989 households and 6,090 individuals interviewed first in 2013), and the SHP_IV (4,380 households and 7,557 individuals interviewed first in 2020).
The panel survey is conducted annually from September to February by the institute M.I.S. Trend in Lausanne and Bern. Interviews are conducted in (Swiss) German, French, and Italian. The standard interviews require around 15 minutes to administer the grid and the household questionnaire and around 35 minutes to complete the individual questionnaire. The main mode of interview is computer-assisted telephone interviewing (CATI). Since 2010 (wave 12), the SHP also offers computer assisted personal interviewing (CAPI) and computer assisted web interviewing (CAWI) as alternative survey modes to those who initially refused to participate.
Alternative modes were also offered in the first wave of the SHP_III sample, which was no longer based on the telephone registry; if no telephone number was available, an interviewer visited the home and respondents completed the household questionnaire by CAPI. The biographical questionnaire (Life History Calendar) in the first wave of the SHP_III was self-administered or administered with an interviewer present.
A two-wave pilot study was conducted in 2017 and 2018, designed to test the consequences of including web as a main mode in the data collection in terms of data quality and comparability between modes. Following the study, SHP_IV was launched in mixed mode CATI-CAWI (about half and half) in 2020: households with a known telephone number are approached for a telephone interview and if no number is available, they are invited to complete the questionnaires by web.