The percentage of Americans who are categorized as "post-Christian" has increased from 37 percent in 2013 to 44 percent in 2015, with the highest percentages residing in urban areas of the northeast and Pacific Northwest, according to a Barna Group study published this month.
"Across the United States, cities in every state are becoming more post-Christian — some at a faster rate than others," the study reveals.
While 78 percent of Americans identify as Christian, Barna used 15 metrics to track indifference to Christianity, and those surveyed had to meet nine of those factors to qualify as post-Christian. Individuals who met 12 or more of the factors are categorized as "highly post-Christian."
Some of the factors used to gauge categories included "whether individuals identify as atheist, have never made a commitment to Jesus, have not attended church in the last year, or have not read the Bible in the last week."
The highest ranked post-Christian cities include San Francisco (66 percent); Albany, New York (66 percent); Boston (65 percent); and Burlington, Vermont (64 percent).
America's most Christian influenced cities are all in the South, but they still experienced a slight decline in movement away from Christianity.
Added to this year's list of top 15 post-Christian cities are: Las Vegas; Fort Meyers-Naples, Florida; Chicago; and Los Angeles. Las Vegas had the most striking growth of post-Christian identification with a jump of 16 percentage points from 2013.
The nation's capital, Washington D.C., ranks 29th on the list with exactly half of its residents identifying as post-Christian.
"The South and Midwest have both lower comparative, and slower rates of post-Christian growth," the report states. "This is inline with these regions' typically higher rates of church attendance and self-identified Christians."
Residents of Shreveport, Louisiana, and Montgomery, Alabama, are the most likely to rate their faith as "very important." And Birmingham, Alabama, is ranked in the top spot for most "Bible-minded city."
Russell Moore, president of the Southern Baptist Convention's Ethics & Religious Liberty Commission, has written a new book titled Onward, where he addresses the role of the Church in the decline of nominal Christianity. In an article published in May titled "Is America Post-Christian?" he writes:
"If we take the opportunity to be the church, we may find that America is not 'post-Christian,' but is instead maybe 'pre-Christian.' It may be that this land is filled with people who, though often Christ-haunted, have never known the power of the Gospel, yet."
Moore stresses that the "mission of Christ" never calls people to nominal Christianity.
In 2013, The Christian Post reported on the initial Barna survey on post-Christian America, which showed rapid increases in the rise of America's post-Christian demographic.
The new survey states that the recent U.S. Supreme Court decision on same-sex marriage and "the growing tension over religious freedoms" point to trends in secularization. In 2013, Gallup conducted a poll that broke down religious influences by state. Vermont was the least religious state while Mississippi ranked the most religious, with 61 percent of residents saying their faith was "very important" to them.
Many American Christian churches and denominations continue to spend more money and resources toward urban church planting, which is increasingly seen as an untapped mission field.
"People are moving into cities faster than churches are moving into cities," said Tim Keller, pastor of Reedemer Presbyterian Church in New York City, during a 2010 speech for the Lausanne Movement in South Africa on urban church planting.
Keller has pointed out that urban churches need to be better focused on integrating vocation and faith because many people move to cities for the purpose of work.
The Barna survey, which features the religious characteristics of adults, was conducted over a seven year period and included over 60,000 individuals.