That and the typical IFB church is gaining membership, and I read (don’t remember where) that the average SBC church has less than 100 members and is in decline.
it is an interesting trend.
To be fair, there are many, many SBC churches--probably too many, I would argue. Many of the smallest churches should probably consolidate with another nearby church (or churches). I understand that in some areas, this isn't possible, but it really doesn't make a lot of sense to have a bunch of small, declining Southern Baptist churches fairly close to each other.
That being said, consolidation might not be the best thing, either. The toxicity of some churches isn't necessarily something anyone would want to spread. Some toxic congregations are churches that may simply need to die off (as a congregation--not the people in it) because they are not honoring God.
But for the small congregations who really do have the right kind of focus on glorifying God but have difficulties with resources, etc---they may need to consider joining hands with other like-minded churches close to them. Sometimes this may mean selling off property, which can generate revenue for kingdom-oriented matters. Very often, churches have enough space to absorb a small congregation entirely without having to invest in any additional facilities, so it could be an economical thing to do (but only if God leads).
It's probably the case, though, that de facto consolidation is in play. Larger churches with more resources often attract people from smaller congregations. I don't think that's necessarily a right or a wrong thing. I do think it should depend on God's leading. People can definitely change churches for frivolous or selfish reasons, but it is also very possible for a person to leave for a larger church because God is calling them to a place where he will use them in a way not available at a smaller church.
That's not to say that large = good. There are many smaller congregations faithfully serving God, and sometimes people even leave larger congregations for these churches because they may be able to serve better there or to become more integrated in a smaller faith community. And if the large church is large but not honoring God, that's another factor. It's simply easier to miss losing a few families in a large congregation than it is to miss them leaving a small congregation.
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Also, and this is very much a speculative generalization here---so I could be
completely wrong---looking at things from the SBC side, it's probably fairly likely that the average IFB church has a higher level of expected commitment than the average SBC church. I've never been a member of an IFB church (or even an attender for more than maybe a handful of times in my entire life), so I'm speaking as an outsider, for sure.
But from my second-hand knowledge of IFB church members and my personal knowledge of SBC churches and ministers, I tend to think that being a member of an average SBC church is probably "easier," for lack of a better term. I say this primarily because IFB churches appear to be further (on average) from the mainstream of evangelical Christianity in terms of worship style, Bible translations, and cultural expectations.
Generally speaking, the further removed something is from social norms, the more difficult it is to retain someone who isn't heavily invested. The average IFB church is probably going to be very counter-cultural, so its growth will likely not come from those following the path of least resistance. If you join an IFB church without having grown up in that environment, you probably are making that choice with the expectation that it won't be the "socially acceptable" thing to do.
SBC churches in conservative regions are probably closer to the social mainstream for the areas in which they are located, so it's not as big of a cultural leap to join an SBC church as it is to join an IFB church. Now, if we go out to liberal areas, joining an SBC church probably would seem pretty far out of the mainstream,and we would be dealing with the same situation as with IFB churches.
Additionally, I think IFB churches on average probably offer a greater deal of certainty in church matters. Some people are attracted to a straightforward approach in church---KJV only or KJV preferred congregations have a sense of common conviction that appears to be stronger than the flexibility of churches that are open to a variety of modern versions. I say this as someone who prefers the ESV, NASB, and CSB, too.
It doesn't mean that preferring the KJV is right or wrong, but I think that someone would err to think that a congregation strongly committed to a belief that the KJV is THE best (or even the only legitimate) translation in English wouldn't also gain a sense of cohesiveness in its community as a result.
The same goes for beliefs on alcohol consumption, attitudes toward aspects of secular culture, etc. If you have a sense of unified certainty, that creates a sense of community that you can't otherwise replicate.
Again, I'm not saying that any of these things are necessarily good or bad--a community can have cohesiveness around terrible things, neutral things, or great things. But the SBC's model as a "big tent" denomination does make things kind of fuzzy.
For instance, if an SBC church is trying to thread the needle in terms of worship style, it very well may alienate most of the congregation by not being traditional enough or contemporary enough at the same time. Theologically, an SBC church may very well have a pastor who is a 5-point Calvinist tending toward Covenant Theology leading a church that is all over the map soteriologically speaking with a strong tendency toward Dispensationalism.
That's not to say that IFB churches are monolithic on these points, but I think there is probably less of a spectrum in the average IFB congregation.
Anyway, I should probably put an end to this meandering thesis.