New research by the Barna group paints an interesting picture of those who are aware of the church and even think positively of the Christian faith, but who, for whatever reason, feel that actively being a part of church is not for them.
'Churchless' is the title of Barna's latest research into understanding today's unchurched and how to connect with them.
The research reveals that the number of churchless Americans has risen sharply since the early 1990s, when only around two out of 10 adults were churchless.
That figure rose to three in 10 in the early 2000s and today now stands at nearly half the adult population (49 per cent).
Those who do not currently have never attended church make up 10 per cent of the population but a far higher figure is the de-churched - those who were once active in church but are no longer - who make up exactly a third of American adults.
Eight per cent of the population are "minimally churched" - they attend church "infrequently and unpredictably".
"Not too many years ago, church attendance and basic Bible literacy were the cultural norm. Being a Christian didn't feel like swimming against the cultural current. But now?" said Barna.
"Churchless confirms that the world has, indeed, altered in significant ways during the last few decades. It's not just your imagination."
In total, there are around 156 million adults and children in the US who are churchles, with more than half of those born between 1984 and 2002 being unchurched, compared to just a third of those born before 1946.
And Barna warns that much of what is reported as "church growth" is actually little more than "transfer growth", where people just change from one church to another, and not from non-Christian to Christ-follower.
"If churches hope to grow by discipling new believers, we must improve our ability to attract those who are intentionally avoiding a connection with the church," said Barna.
The younger the person is, the more likely it is they have never been to church and are 'post-Christian' - lack any Christian identity, belief and practice.
But the door hasn't been completely shut, with two in three unchurched Americans describing themselves as spiritual, and six in ten churchless adults saying they prayed in the last week.
"The truth is, most of them are already looking for a connection with God," Barna said.
Three-quarters of unchurched Americans say they own a Bible and two-thirds said they tried to grow spiritually in the past month by talking about faith with friends and family, or by watching religious TV programming.
The research reveals the scale of the challenge facing the church, as 99 per cent of the unchurched said they were aware of Christianity and over two-thirds (69 per cent) said they had a favourable view of the faith. And yet nearly half also said they see no value in personally attending church.
Barna has made a full colour infographic for use in church sermons available to download here