Switzerland's population is being counted in the most expensive census ever. Critics say the SFr150 million exercise is old-fashioned and unnecessary and that all the data needed is already on local registers.
Most Swiss residents are likely to find that their census forms have already been partly filled out by the federal statistics office, with information supplied by local authorities.
But Werner Haug, who is organising the census, says the information is not complete and that the office is working on improving the situation.
"We are investing in the development of these registers, especially the dwelling and building registers, but also registers of population, because they are non-existent or badly harmonised in Switzerland," he told swissinfo.
The statisticians also want to gather much more information than will ever be available on local registers. Swiss residents are being asked how much housework and other unpaid work they do, and what language they think in.
Everyone living in Switzerland on Tuesday, December 5, is required to answer the questions in the census, which is carried out every 10 years.
Haug says it is important for the authorities to gain as complete a picture as possible about the make-up of the population and the way it is changing.
Although it will take the statistics office until the end of next year to process the information collected, he says there is no doubt it will reveal some considerable changes over the 1990 census.
"There has been a lot of immigration, and the linguistic and religious structure of the population, especially in the big cities, has changed quite a lot. There are also the effects of structural changes in the economy, with new jobs and new professions.
"And finally, the settlement structure has changed quite a lot due to the development of transportation and communications."
For the first time in Europe, residents will be able to file their details on the Internet. It is also the first time a private company, Data Care, will be participating in the collection of information on behalf of the statistics office.
The Association of Data Protection Ombudsmen has warned that not enough control is being exercised over Data Care to ensure it does not misuse the information, particularly as it could be of major interest to its owners, Swiss Post and Germany's Bertelsmann.
However, Haug says Data Care's staff is obliged to follow the same rules of confidentiality as the statistics office's own employees. He says the company also cannot afford to make any mistakes, or its reputation and business would be ruined.
The census is a complex logistical exercise. More than 12 million forms in the four national languages have been sent out by post to about 94 per cent of the population. In small communities, the traditional enumerators will be going from door to door.
A special hotline has been set up to help answer questions and to provide translations in 10 languages, and SFr4.5 million has been invested in the Internet site.
Haug says that if the local registers can be developed as planned, this could be the last big national census. Continuous information would be available on the basic data, while the detailed information could be gathered in surveys of a representative sample of the population.
"Moving away entirely from such a big exercise is one of the possible scenarios," Haug said. "Putting together all the data available at one moment in time will always be necessary, but the data collection methods will certainly change very much."
by Malcolm Shearmur