Christians overall remain a large majority in the US, at nearly 70 percent of Americans. However, white Christians, once predominant in the country's religious life, now comprise only 43 per cent of the population, according to the Public Religion Research Institute, or PRRI, a polling organisation based in Washington.
Four decades ago, about eight in 10 Americans were white Christians.
The change has occurred across the spectrum of Christian traditions in the US, including sharp drops in membership in predominantly white mainline Protestant denominations such as Presbyterians and Lutherans; an increasing Latino presence in the Roman Catholic Church as some non-Hispanic white Catholics leave; and shrinking ranks of white evangelicals, who until recently had been viewed as immune to decline.
President Donald Trump, who repeatedly promised to protect the religious liberty of Christians, drew 80 per cent of votes by white evangelicals, a constituency that remains among his strongest supporters.
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About 17 per cent of Americans now identify as white evangelical, compared to 23 per cent a decade ago, according to the survey. Membership in the conservative Southern Baptist Convention, the largest US Protestant group, dropped to 15.2 million last year, its lowest number since 1990, according to an analysis by Chuck Kelley, president of the New Orleans Baptist Theological Seminary.
The PRRI survey of more than 100,000 people was conducted from January 2016 to January of this year and has a margin of error of plus or minus 0.4 percentage points. Previous surveys had found that the Protestant majority that shaped the nation's history had dropped below 50 per cent sometime around 2008.
The PRRI poll released today included a more in-depth focus on race and religion. Jones said growth among Latino Christians, and stability in the numbers of African-American Christians, had partly obscured the decline among white Christians.