One of the questions we have to address in documenting (and even assessing, auditing, evaluating, etc.) movements is how to count the number of people in them.
Movements are another form of a group of churches--a network or denomination. Movements have some unique characteristics, chiefly around rapid growth. Most would probably never want to be called a denomination, but the term is not entirely without validity.
The word denomination originated somewhere around the 14th century and comes from the two roots de("completely") and nominare ("to name"). A denomination from the mid 15th century was "a class name" or "collective designation of things"; which rapidly became (a) a religious sect ("Baptists, Lutherans, Methodists, etc") and (b) a monetary classification ($20 dollar bills or $100 bills, etc).
Christian denominations are made up of churches, which are in turn made up of people. How do we count the number of churches and people? It's not as simple as going from church to church and counting up the number of people "in the church."
To begin with, which people within the church count?
1. Some churches count Sunday morning attendance ("We have about 1,000 people in Sunday morning worship"). The flaw with this method: there can be non-believers in the service, so you're not getting an exact number of Christians.
2. Some churches count baptized church members. The challenge with this, in a denomination as a whole, is that some people are baptized and then, for one reason or another, leave the denomination.
a) they may no longer go to church. It might be a case of backsliding, or it might be a case of advancing age, or it might be a case of a health crisis or some other stage in their life.
b) they might transfer to a different church, or transfer to a different city, state or country, but not be struck from the membership rolls.
3. Some churches only count adults, while others count both adults and children. This can lead to a significant difference when comparing two denominations.
Further, the numbers of members are constantly in flux. New people are being born. New converts are being baptized. Children are becoming adults. Some people die. You can have a more or less "exact" number as of some specific day in some specific year, and 24 hours later that number could very well have changed.
Some denominations have a specific methodology for taking a count, and they ask their churches to turn in that number as of a specific date of the year. Other denominations have a much more haphazard approach. But the discussion above illustrates why we should never consider "number" so obtained to be very exact, and why we should always be aware of the methodology of counting when comparing one denomination to another. I'm not saying the "numbers" are invalid: we just need to know how they are obtained and what they mean. Some denominations will have to have their numbers adjusted to make for an "apples to apples" comparison (e.g. churches that count only adults will have to be adjusted to compare to churches that count both adults and children).
Obviously, there are theological implications of these points. As an illustration of such discussions, check this article (I just Googled quickly for it; I'm sure other denominations have other examples).
The task is yet more complex. Denominations have to count the number of churches, and these, too, change over time. Churches are planted, and churches die. In some cases churches can leave one denomination and join another; in other cases, churches can be disfellowshipped from one part of a denomination, yet remain part of a larger denominational network (e.g. a Southern Baptist church could be disfellowshipped from a State convention, yet retain its name, and remain part of the National denomination). So simply asking 'how many churches are in the denomination' is not always a straight-forward thing.
In movements, this whole process is far more difficult than in many Western denominations, because:
1. Movements are aggressively growing through outreach. What is the line where a person moves from being a seeker to being a believer? Especially in contexts where baptism might be postponed for a while? In some countries, some groups have a theology that insists only a certain type of minister can baptize people, and this mean that hundreds, thousands, or tens of thousands of believers are still waiting for baptism. In some movements, there are long periods of time where people are discipled, and their commitment seen before baptism is "offered"; are these people believers even though they have not yet been baptized? Movements have to deal internally with these theological issues.
2. In many places, there are significant family issues that affect counting. In most Western environments, if the "father" becomes a believer, that doesn't mean the wife or the children are automatically counted. In other environments, if a Christian woman with children (e.g. perhaps a widow) marries a Muslim man, her children (and often her) are automatically counted as now "Muslim." If the head of house becomes a Christian, what happens to families? These are thorny issues that impact counts.
3. Many movements feature "seeker groups" that eventually become "house churches." What is the line where a "group" becomes a "church"? When do they get counted? Different movements will deal with this in different ways.
4. Given the enormous numbers of groups/churches being planted through viral reproduction, how do they get counted? When a movement consists of just 4 generations, it's usually easy to know how many groups there are. When a movement reaches 6th generation or higher, it becomes exponentially more difficult.
5. Further difficulties arise as churches split (divide-to-multiply), migrate (as people migrate to different areas for work), die (stop meeting for any of a variety of reasons), etc. Tracking all of these popping and moving bubbles of activity is obviously very challenging.
6. Another issue is security - simply collecting data on lists can be very problematic in some areas.
Even though movements face big challenges in counting these numbers, we shouldn't think that they are somehow more challenging or less accurate than Western churches. For the reasons noted above, it's well known that many Western denominations have difficult counts as well. For an interesting but more academic look at some of the methodological difficulties the Southern Baptists face (and I chose this just because it showed up first on a Google search), see this research paper.
Counting is a difficult process, but if the basic challenges are understood, they can be methodologically dealt with. Having surveyed some of the issues in this background post, I'll be writing about some approaches to counting churches in movements over the next few blog posts.