Geneva -- The number of Swiss residents who say they have no religious affiliation has increased sharply over the past three decades, and the country's two traditional churches are feeling the effects.

More than 11 per cent of the country's 7.3 million population belong to no religious group, according to the 2000 census report recently published by the Federal Statistics Office. In 1970, this category accounted for only about 1 per cent of the population.

The drop in religious affiliation is a particularly urban phenomenon, with twice as many city dwellers as rural residents claiming no religious identity. People aged 30 to 50 - at the height of their professional and social lives - also showed a tendency not to belong to any religious body.

This disengagement explains in part the loss in membership of Switzerland's two main churches, the Roman Catholic and the Protestant Reformed, according to the census report, dated 30 January.

The Roman Catholic Church today claims the loyalty of 41.8 per cent of the population - a drop from 46 per cent in 1990, when the last census data were collected. The Reformed church claims 33 per cent - down from almost 39 per cent in 1990.

At the same time, however, religious communities almost unknown to Switzerland 30 years ago have increased their numbers dramatically with the arrival of new immigrants in the country. Today these religious groups account for about 7 per cent of the population. In 1970, they represented less than 1 per cent.

Islam and Orthodox Christianity, the most prominent among them, have doubled their numbers in the past decade - "a direct consequence of immigration" from the former Yugoslavia, according to the census report.

Islam accounts for 4.3 per cent of the population and Orthodox Christianity 1.8 per cent.

Families of the religious groups new to Switzerland tend to have more children than the established communities, according to the report, and their religious communities "therefore clearly have a higher growth potential".

The membership of the traditional churches, in contrast, is getting older, the report said, particularly that of the Reformed church.

Switzerland is one of the few European countries to include a question about religious affiliation in its census, and more residents refused to give their religious affiliation in 2000 than previously.

For foreigners especially, religious affiliation is considered a private affair, commented the report. In addition, households with mixed marriages have increased, and parents have difficulty in defining their children's religion, it said.

By Laurie Spurr