From this Religion News Service discussion w/ Frank Newport, editor-in-chief of The Gallup Poll, on church growth and decline in America:
Q: You write that mainline Protestants are pretty much doing everything wrong in terms of growing their churches. Why’s that?
A: For any group to grow, whether it’s a country or a church, you have to have more people coming in than going out. For example, the Catholic Church holds its own in terms of percentage of the American population because of the in-migration of Hispanics. But there is no massive in-migration of Protestants. Secondly, there’s been no evidence that they’ve been able to evangelize effectively. And thirdly, one way you grow is to have high fertility rates. Mormons are doing that well because their theology encourages big families. But Presbyterians, for example, have less children on average (than other Americans).
So, if you look at all the ways churches could grow, the mainline Protestants haven’t been able to hit the nail on the head with any of them.
Q: Is there any evidence that mainline Protestants’ fierce debates over homosexuality are costing them church members?
A: That’s an interesting hypothesis that you hear a lot: Nondenominational churches can focus more on active ministry to parishioners, while mainline churches’ annual meetings are spent arguing these issues. But the empirical data on that is lacking. It certainly seems to be a viable hypothesis.
Newport’s information is based on over a million interviews conducted by Gallup since 2008.