Nationally the Southern Baptists are the second largest church in America.
Those that are on the rolls, or those that show up regularly on a Sunday?
Southern Baptists, and other Baptists to the best of my knowledge, remove you from membership if you stop attending.
I know there are other churches that claim you from birth to death and perhaps after, no matter what you do, but I think that with the Baptists you have to stay on their rolls actively, or you get removed from their count.