For over half a century, Gallup has been asking Americans whether they think the influence of religion is increasing or decreasing in the U.S., posing the intriguing question of what the results actually signify.

For starters, it’s worth bearing in mind that Western civilization is grounded in the belief that once upon a time, God was in his heaven and people went to church regularly. So at any given time, more Americans are likely to think the influence of religion is in decline than the other way around.

That said, what accounts for the rather striking ups and downs in the chart? In its latest release, Gallup emphasizes that these do not reflect changes in personal religiosity — and I’m inclined to agree, up to a point. Here’s the story I’d tell about the people’s perception of religion’s influence.