This bit from the Times (UK)
The 'yes' vote, if confirmed, shows the strength of feeling against a Muslim population which has grown over the past 20 years to 350,000 or four per cent of the population. The majority are not regular practitioners of their faith. Most are from Turkey and the Balkans.
Only four modest-sized minarets exist in Switzerland, where there are 150 prayer houses. None are used to call the faithful to prayer.
reminded me of something I read long ago, in one of Studs Terkel's oral histories. A police officer in a midwestern US city talks about how "coloureds" are "taking over" the department. Terkel's footnote says that three percent of the department is now non-white.
Further back, from a university psychology class, I remember a researcher investigating what percentage of people of colour could be present in a social setting before the majority of white people in the room felt uncomfortable. It was under 10%. The study was done in 1970s United States, but you can make your own substitutions for hijabs and mosques.