Data collection mode: Standardized face to face Interviews, CAPI (Computer Aided Personal Interviewing) Sample: Swiss resident population aged 15 and over, living in private households, who speak one of the main national languages (German, French or Italian). No upper age limit. Sampling: Single stage equal probability systematic sample (no clustering); the sampling is done by the Swiss Federal Statistical Office out of the register sample frame - Gross sample size: 4863 - Net sample size (without ineligibles): 4569 - Interviews: 2141 (Response rate=46.86%) Design: - cross-sectional, repeteaded every 2 years, part of the questionnaire being identical - Fieldwork period: 15.09.04 - 28.02.05 Fieldwork institute: M.I.S. Trend SA, Lausanne No weighting, all weight=1, according to the sample design (all respondents have the same probability to be selected)