In a couple of weeks I will be taking my annual vacation and this year I will have to pack light.  No thick volumes on the ecumenical movement or church history this year.  After looking around and thinking about this I decided to take along for reading several of the articles in a collection on the Patheos web site on The Future of Mainline Protestantism.  This is an interesting collection of opinions coming almost completely from progressive authors.  I know several of the authors, have heard several more speak, and have read other works by most of the rest.  And based on the skimming I have done so far, they all see a positive future for the mainline.  So check back at the end of the month when I’ll post my thoughts on what I have read from there.

But in preparation for that I have started going through a series of purely mathematical thought exercises about possible numerical futures for the mainline, and specifically the PC(USA).  For the most part these are intended to be disconnected from theological, institutional or political specifics, although the more detailed model at the end does use some of that.  They are also intended to be general concept models that represent particular cases, not specific predictions of the size of the church in fifty years.  On the one hand, I will be making specific calculations based on the numbers for the PC(USA).  On the other hand, these cases apply to more than one of the mainline churches and can probably be applied to other denominations as well. So here is what I have thought about.

Case 1 – Status quo
At the present time the mainline denominations are all declining in membership at the rate of a few percent per year.  Clearly if this continues into the future each will reach a point where that church will not be viable.

For example, for 2009 the PC(USA) reported a total membership of 2,077,138, a net loss of 63,027 from the year before.  A quick calculation shows that with a constant loss of this many members the denomination would reach zero in 33 years in 2042.

As you can probably figure out this is not realistic for a number of reasons, some of which I’ll talk about in the last, and most complex, model.  A better way to look at the status quo is to consider a constant rate of loss.  In 2008 the rate was 3% and in 2009 it was 2.9% so if we look at three different constant rates – 2.5%, 3.0% and 3.5% – this is what we get for the PC(USA).

Year	Constant Number	Constant Rate
	63,027/yr	2.5%/yr	3.0%/yr	3.5%/yr
2010	2,014,011	2,025,210	2,014,824	2,004,438
2020	1,383,841	1,572,230	1,485,780	1,403,673
2030	753,571	1,220,569	1,095,650	982,967
2040	123,301	947,564	807,959	688,354
2042	0	900,778	760,208	641,013
2050		735,622	595,808	482,042
2060		571,085	439,363	337,566

Case 2 – Renewed Growth
I saw you roll your eyes at this one.  Yes, there is a case to be made that the mainline represents an out-dated model that will not survive but rather decay into oblivion as outlined in Case 1.

But remember that this is only a thought experiment.  Furthermore, while there is a denomination-wide decline in church membership, on a congregation-by-congregation level this is not necessarily so.  Several congregations in my presbytery have shown stable membership over the last ten years (example 1, example 2, example 3 ). (And I will note that this crosses theological lines.)  In addition, every so often a national entity issues a list of growing PC(USA) churches and there is a general document abut the characteristics of the fastest growing churches.  I could not quickly find that list (I’ll update here if I do) but checking three high-profile congregations I found recent (5-10 year) growth rates of 11.0%, 3.5%, and 2.6%.  This is not a scientific sample of growing churches, only a few that I checked.  The point is that the decline is not uniform across all the congregations in the PC(USA) and that is probably true of other mainline churches as well.  In fact, there is a book out there (that I have not read) that looks at 15 growing Presbyterian churches and why they are growing.

Now, without my actually saying what needs to be done to reverse the decline and begin growing, let me present the model for this case that would propose that a mainline church can get itself organized and take steps to help enough congregations reverse their decline and begin growing in the next decade so that beginning in 2020 the denomination as a whole can begin growing at 1% per year.

(The disclaimers: I am not advocating anything specific at this time, and especially not advocating a cookie-cutter one-size-fits-all franchise scheme for the mainline denominations that would produce a business plan for homogenous churches that are all the same. And I do know that the PC(USA) has been working on doing this one way or another, with out a reversal of the membership decline, for years now. I am also well aware of some of the other complexities of church growth these days, such as the argument that when churches grow all they are really doing is attracting members that are leaving other churches so church growth in many cases is competition for a limited, and declining, resource.  Remember, this is just a thought experiment.)

So here is what the reversal model looks like:

Year	Annual Growth Rate	Membership
2009		2,077,138
2010	-3.0%	2,014,824
2011	-2.6%	1,962,438
2012	-2.2%	1,919,265
2013	-1.8%	1,884,718
2014	-1.4%	1,858,332
2015	-1.0%	1,839,749
2016	-0.6%	1,828,710
2017	-0.2%	1,825,053
2018	0.2%	1,828,703
2019	0.6%	1,839,675
2020	1.0%	1,858,072
2030	1.0%	2,052,467
2040	1.0%	2,267,201
2050	1.0%	2,504,400
2060	1.0%	2,766,416

Case 3 – Partitioning or Pruning Model
What if, to use the cliche, we are “right-sizing” the mainline.  Consider that the decline in the churches will continue until the target size is reached and then the membership will reach a stable equilibrium.

Well, that is the idea in the abstract but to actually crank out some numbers here I will have to propose certain conditions that I can model.  Taking the conventional wisdom that the mainline is becoming more liberal or progressive, why don’t we set as a target size the number of liberals in the church suggesting that all the conservatives will eventually be departing one way or another.

For the PC(USA) I have previously commented on the changes seen in the Presbyterian Panel surveys. (Sorry with the change in the PC(USA) web site links in that post to some of those data sources are now broken and I am trying to restore them.)  By one measure, in 2008 34% of the PC(USA) considered itself theologically conservative, 41% moderate, and 25% liberal.  Another measure is the question of whether “Only followers of Jesus Christ can be saved” where 39% agreed, 25% were not sure, and 36% disagreed.

Now, as a simple first-order model what if we say the evangelicals leave, the progressives say and the moderates split.  There is some symmetry in the survey results so for the sake of argument let’s say that the denomination’s target size is 50% of the 2009 membership and that the total membership loss rate of 3% per year comes completely from the half that is experiencing the departures so we reduce the size of those in the group that remain by 6% per year.  This is then constant rate of decline for part of the church and no decline for the other with the total size slowly approaching the target size.  Numerically this wold look like:

Year	Membership
2009	2,077,138
2010	2,014,824
2020	1,564,395
2030	1,321,787
2040	1,191,114
2050	1,120,732
2060	1,082,823
Target	1,038,569

Case 3a – Complex Partitioning or Multiple Effect
OK, as a final model let us leave the realm of first-order models and consider something with two levels of complexity. As those that have looked at membership statistics know, there are many different factors involved in the mainline decline.  For this model let us take the 3% decline of the Partition Model and say that 2.5% of that is theology-based departures and it gets applied fully to the declining group.  Let us also say that there is a 0.5% decrease for other reasons – cultural, political, social – all lumped into that one decline.  This decline is applied uniformly to both groups.  (I arrived at this 0.5% number from looking at general rates of decline of Protestant denominations in the American Religious Identification Survey.)  So now, instead of “right-sizing” the denomination to a fixed target size we have a model where the membership is rapidly declining towards a target size that is declining itself, but at a much slower rate.

Year	Membership
2009	2,077,138
2010	2,014,824
2020	1,540,278
2030	1,251,397
2040	1,068,914
2050	947,759
2060	862,294

Putting it all together
Here is a chart showing the five different models for direct comparison.

Closing words and Commentary
As I wrap this up I should probably repeat again that these are mostly first-order models that use constant or smooth variations in the constants.  Other cases could be developed for the rapid departure of particular groups or for the outright division of the church.  And while I have modeled the partitioning into two groups you could also imagine the case where it is best modeled as three groups – conservatives, moderates and liberals each in their own partition, or maybe conservatives, emergents, and everyone else.

Having put all of these forward I will state that my own leaning at the present time is to view the future of the PC(USA), and probably some other mainline churches, as following a hybrid model where the church experiences a partition decline coupled with a general decline model.  But I think at some time, and maybe not in the next 50 years, the church will reach a “right-size” or equilibrium state where membership will hold fairly steady.  But based on these models I will say that the current PC(USA), and similar churches, will not look anything like the present church in size or structure.  Time will tell if this is right and what the church will actually look like.

But having said what I expect to happen, let me also say that I am praying for the reversal model.  I look to God to find a way for the PC(USA) and other churches to move beyond the current divisions and find a way to bring the Gospel to the world in such a way that people are attracted to the church and the numbers grow again.  It does occur to me that maybe this would require partition in order for the witness to begin again and the churches to grow.  I don’t know what the answer is but I pray we are attentive to God’s leading as we honestly and prayerfully discern together where we are going.

Now on to another general look at this sort of thing from a different angle, coming up in two or three days.