The study, carried out by a Basel-based advisory body on behalf of the Swiss federal migration office (SEM), estimates there to be 76,000 illegal immigrants in Switzerland, down from around 90,000 ten years ago.
“We emphasize that this is an estimation,” the study's authors said. “The number of illegals cannot be established with certainty, but is probably between 50,000 and 90,000.”
Some 43 percent come from central and south America – the largest geographic group – and 24 percent from European countries outside the EU.
Two-thirds arrived in Switzerland as tourists or without travel documents, while a fifth became illegal when they failed to leave Switzerland after their application for residency or asylum was rejected.
Some 28,000 live in Zurich, with 13,000 in Geneva and 12,000 in the canton of Vaud. By contrast only around 600 live in the Italian-speaking canton of Ticino.
The small number in Ticino “can be explained by the availability of Italian cross-border workers coming to work in Switzerland,” said the study, meaning there are fewer jobs available to illegals.
Overall across the country, nine out of ten adult illegal immigrants are in work, said the study, though many experience precarious conditions, working long hours for low pay.
Half of them work in private households, while many others are employed by the construction and hospitality industries, it said.
Working in a private house is attractive to many illegals because it can fit around their children's school hours, the study said.
And private employers like giving them work because it allows them to “reconcile the useful (cheap labour) with the agreeable (helping illegals)” one specialist told the study.
The situation also works for small businesses that can offer low salaries to illegals, said the study.
The study gathered information from different sources including interviews with 60 experts in 12 cantons, data from a central migration information system and federal statistics.
Similar research carried out ten years ago concluded that illegal immigration was linked more to the employment market than to Switzerland's asylum policy.