Their perception is that churches are too concerned with money and power, focused on rules and overly involved in politics.

Interestingly, nearly half of religiously active Americans agree with those criticisms. For the first time, less than half of Americans call themselves Protestants. In 2007, 53% identified themselves as Protestant, but only 48% did so in 2012.

In the past, declines were concentrated among white mainline Protestants, while white evangelicals were growing. Now both are in decline. Black Protestants remain unchanged.

The Catholic share of the population has held steady at 22% of the population, with significant additional numbers of Hispanics offsetting fewer young people in church.

What's rising rapidly are what demographers call the "nones," people with no religious affiliation. Why?

Pew cites "generational replacement," the substituting of an older, religiously active generation with a less interested young generation. A third of those aged 18-22 are unaffiliated vs. only 9% of the "Silent Generation," born before 1945.

However, there has also been a significant increase in the unaffiliated among Baby Boomers, rising from 12% in 2007 to 15% and among Generation Xers, increasing from 18% to 21%.

By another measure, a similar trend can be seen in church attendance which has fallen. In 2003, a quarter of all Americans said they seldom or never attended services, which grew by 4 points to 29% by 2012.

In 1987, 88% of Americans said they never doubt the existence of God. By 2012, that figure was down to 80%.

The growth of the unaffiliated has been across a wide variety of demographic groups - among both men and women, college graduates and those without a college degree, plus among those earning more than $75,000 and less than $30,000, and in all parts of the nation.

The unaffiliated "are not uniformly hostile" toward religious institutions. Three-quarters acknowledge that churches bring people together, strengthen community bonds and play an important role in helping the poor and needy.

However, only half of the religiously inactive believe that religious institutions "protect and strengthen morality," while eight in ten of the religiously active are convinced of that role by churches.

America remains vastly more religious than other advanced industrial democracies. Three in five Americans say religion is "very important" in their lives - more than triple the British (17%) or French (13%) who feel similarly.

Yet the erosion of believers should be a cause of concern for all churches.

What can be done?

One of the most successful pastors in America is Rick Warren. He built Saddleback Church in Orange County, California from a handful meeting for a weekly Bible study in 1980 into a church that gathers 20,000 each week, America's eighth largest church.

From the very beginning he sought out the unchurched. He quotes Jesus: "It is not the healthy who need a doctor, but the sick. I have not come to call the righteous, but sinners."

Consequently, he went door to door talking to people. He asked what their most pressing needs were. "People don't care how much we know until they know how much we care," he wrote in his landmark book, "The Purpose-Driven Church."

Prior to his first Sunday service on Easter, he and his 15 early followers wrote 15,000 letters and mailed them 10 days before Easter, hoping that 1 percent might respond, 150 people. On Palm Sunday, he practiced his service at the local high school. To his delight, 60 showed up for the dress rehearsal and 205 on Easter.

He shared "The Saddleback Vision" in his first sermon, as "the dream of a place where the hurting, the depressed, the frustrated and the confused can find love, acceptance, help, hope, forgiveness, guidance and encouragement.

"It is the dream of welcoming 20,000 members into the fellowship of our church family - loving, learning, laughing, and living in harmony together. It is the dream of equipping every believer for a significant ministry by helping them discover the gifts and talents God gave them."

There's hope. The unchurched can be reached.

Michael J. McManus, President of Marriage Savers and a syndicated columnist