The national news media yawned over the Baylor Survey's findings that the number of American atheists has remained steady at 4% since 1944, and that church membership has reached an all-time high. But when a study by the Barna Research Group claimed that young people under 30 are deserting the church in droves, it made headlines and newscasts across the nation—even though it was a false alarm.

Surveys always find that younger people are less likely to attend church, yet this...