The NES’s methodological basis is a survey of 4 times 5,000 people that is distributed across the year. The NES universe comprises the permanent language-assimilated resident population of Switzerland and the Principality of Liechtenstein that is aged 14 or older. Every quarter of a year, participants are selected using a multi-step random process (geographical sample points, households, persons) based on the complete address directory of Swiss Post. Households with landlines are surveyed by phone; others receive a printed survey by post with the possiblity to complete it also online. Each phone interview lasts a maximum of seven minutes. Institut M.I S. Trend, Lausanne, is charged with performing the field work.