[calvinmorrison]

> while the other half is explained by people who still attend church regularly, but avoid formal "membership" in a congregation.

I wonder if this can be explained by an increase in people moving around compared to a hundred years ago. I am a member of the church I was raised in, but I am not local enough attend. I do visit when I am with my parents but otherwise it doesn't make sense. I wouldn't go join another church though - even though I do attend other services in my city, I am not a member at those churches

[dbatten]

Yeah, likely part of it. I think there's also been a rise in non-denominational and "seeker-sensitive" churches that just don't have any concept of membership at all...