A new study on American religion finds that Catholicism is facing a “stunning” decline in the northeast United States as the population center of U.S. Catholics shifts towards the southwest. Secularism continues to grow in all regions, while mainline Protestant denominations face the most significant population decline.

The study, titled the American Religious Identification Survey (ARIS), was conducted by the Program on Public Values at Trinity College.

According to the ARIS report, Catholic numbers and percentages rose in many states in the South and West mainly due to immigration.

“Catholics increased their share in California and Texas to about one-third of the adult population and in Florida to over one-fourth. In terms of numbers they gained about 8 million adherents in these three states in the past two decades,” the report says.

In the Northeast, Catholic adherents fell from 46 percent to 36 percent of the adult population.

“New England had a net loss of one million Catholics. Big losses in both the number of Catholic adherents and their proportion occurred also in Massachusetts, and in Rhode Island, the nation’s most heavily Catholic state where the proportion of Catholics dropped from 62 percent to 46 percent. New York state lost 800,000 Catholics and they dropped from 44% to 37% of the adult population.”

“The decline of Catholicism in the Northeast is nothing short of stunning,” said Barry Kosmin, a principal investigator for ARIS.

The ARIS study estimates that self-identified Catholics in 2008 numbered about 57.2 million, 25.1 percent of the population. This contrasts to about 50.9 million who made up 24.5 percent of the population in 2001, and 46 million who made up 26.2 percent of the population in 1990.

The percentage of Christians in the U.S. declined from 86.2 percent in the 1990s to 76 percent. ARIS attributes 90 percent of the decline to the non-Catholic segment of the Christian population. The mainline Protestant segment, which includes Methodists, Lutherans, Presbyterians, Episcopalians/Anglicans, and the United Church of Christ, particularly declined. They constitute just 12.9 percent of the population, down from 18.7 percent in 1990 and 17.2 percent in 2001.

Baptists, the largest non-Catholic Christian tradition in the U.S., grew by two million but declined as a percentage of the population.

Among self-described Christians, the number of persons who identified only as “Christian,” “Evangelical/Born Again” or “non-denominational Christian” grew the most. In 1990 they numbered less than 200,000 people, five percent of the U.S. population in 1990, to over 8 million, 11.8 percent of the U.S. population, in 2008.

Mark Silk, director of the Public Values Program, in a statement said the split between mainline and evangelical Christians is “collapsing.”

“A generic form of evangelicalism is emerging as the normative form of non-Catholic Christianity in the United States,” he said.

The percentage of Americans claiming no religion jumped from 8.2 percent in 1990 to 14.2 percent in 2001. Their numbers have increased to 15 percent, with Northern New England now the least religious section of the country.

“The ‘Nones’ are the only group to have grown in every state of the Union,” said study investigator Ariela Keysar.

The study reports that only 69.5 percent of Americans say there is “definitely a personal God.” About 12.1 percent professed belief in a “higher power” but not a personal God. Only 2.3 percent of respondents denied the existence of God, while about ten percent professed uncertainty or said there was no way to know if God exists.

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