''Even though immigration is increasing diversity,'' Luis Lugo said, ''its primary result is that it's reinforcing the Christian character of American society.''

Lugo presented findings from Pew's sweeping U.S. Religious Landscape Survey to some 240 Catholic bishops attending their annual spring meeting.

The survey, first released last February, measured the changing and diversifying religious affiliations of some 35,000 American adults. Researchers found that Catholics lose more adherents than any other religious group; one in 10 Americans are former Catholics.

Despite those losses, Catholic numbers have held steady during the last two decades, at about a quarter of the U.S. population. That's thanks in large part to immigrants, notably Latinos. About one-third of U.S. Catholics are Latino, which is helping offset the more secular attitudes that have gained ground in Europe, Lugo said.

''Immigration is not leading to the de-Christianization of American society but to the de-Europization of American Christianity,'' said Lugo, a native of Cuba.