Churchgoing is slowly but undeniably losing its role as a normative part of American life. Recently our team at Barna Group has been examining the unchurched—who they are and how they are changing—by poring over three decades of research on the churchless. We have uncovered a number of trends.

First, the unchurched population is steadily growing. Since 1990, it has jumped from 30 percent of U.S. adults to 43 percent today. (We define unchurched as anyone who hasn't been to a church in the last six months, excluding weddings and funerals.) It's important to remember that while this segment has grown, it is still a minority. Most Americans continue to have some connection to a church, even if only for holidays.

Second, the number of people who have never been active churchgoers has increased. In the last two decades, the never-churched increased from 15 percent to 23 percent. Currently, one in four Americans has virtually no personal history of church participation. ...