CHICAGO (Reuters) - American Muslims grew in number over the past decade, outnumbering Jews for the first time in most of the Midwest and part of the South, while most mainline churches lost adherents, according to a census of American religions released on Tuesday.
The number of Muslim adherents rose to 2.6 million in 2010 from 1 million in 2000, fueled by immigration and conversions, said Dale Jones, a researcher who worked on the study by the Association of Statisticians of American Religious Bodies.
"Christians are the largest group in every state, but some of the things we found interesting was the growth of the Mormons, who reported the largest numerical gain in 26 states," said Jones, who presented the report to a conference in Chicago.
The number of Mormons, whose Utah-based church's formal name is The Church of Jesus Christ of Latter-day Saints, grew by 45 percent to 6.1 million in 2010, according to the census, which asked 236 religions to count their own adherents. Family members of adherents were generally included in the numbers.
Roughly 55 percent of Americans attend services with enough regularity to be counted, according to the data. By comparison, most surveys estimate roughly 85 percent of Americans profess religious faith, though they may not attend services.
Some 158 million Americans were classified as "unclaimed" by any religion in the survey.
Among major religions, the census found the number of Catholics, the largest single faith, declined 5 percent to 58.9 million during the decade.
"Catholics had the largest numeric decline," including big losses in Maine where a priest abuse scandal came to light, Jones said. In the New England region, Catholic funerals are outnumbering baptisms, he added.
Among the other largest U.S. faiths, adherents to the Southern Baptist Convention held steady at 19.9 million over the decade, the United Methodist Church lost 4 percent to 9.9 million adherents, the Evangelical Lutheran Church in America lost 18 percent to 4.2 million, and the Episcopal Church lost 15 percent of its adherents to 1.95 million.
Evangelical protestant congregations continued to grow, though slowly, to 50 million adherents. Most of the growth, surprisingly, was in urban areas and the vast majority of expanding congregations have fewer than 100 members and are not large mega churches, Jones said.
Jones said Buddhists made strong gains in the Rocky Mountain states, where the number of temples and congregations increased markedly. The total number of Buddhist adherents in the United States was nearly 1 million. There was no estimate in 2000.
"Based on some of the temple names, I think some of the upscale yuppie types are looking for something different than the church they grew up in," Jones said.
Editing by Greg McCune and Paul Simao