I've been doing a considerable amount of thinking about "the task" of missions and "when the task is finished." Some of my thinking has been very passionate, and not very structured. In this, I'm going to try and be a little bit more structured. Two comments on "Jesus wants the whole pie" are instructive in this.
First, John Lambert commented "closure is just the beginning" and "yet we have still not made initial breakthroughs in a large number of unreached peoples." This is very true, and it is the driving force behind the work of Finishing the Task and its related groups.
Every group needs to at least be begun in order to be finished. Or, to put it another way: if we don't begin, the task isn't presently "finishable." And there are still lots of peoples where this is the case. Second, Jim comments: "one of the unintended consequences has been the marginalization of Christianity in majority non-Christian populations." He goes on to use the Thai as a classic example (see the original post for a full read). Now, here's a people group - the Thai - that are clearly engaged: there are missionaries among them (although, as Jim notes, there are proportionally far fewer missionaries amongst the majority Thai than amongst the tribals). There's even an indigenous church among them (although quite small compared to other groups). So, are the Thai "reached"? "Finished"?
The classic definition of "reached" is a group having a church that can evangelize the group to its "borders" without cross-cultural assistance. The classic definition of 'reached' is really about whether the role of the cross-cultural missionary is finished. Can I count myself done?
Let's use the Thai church as an example. Is the task of mission done? Are the Thai "reached"? Can the Thai church finish the task without cross-cultural assistance? This is a hard and complex thing to measure. Let's start with a simpler question: Is the Thai church doing this? Jim argues no, and the data seems to me to agree.
Given its current methods and history, organized Christianity in Thailand is growing at 2.99% p.a., according to the 2010 Atlas of Global Christianity. In fact, take this further: over the past century, Christianity has averaged a growth rate of 1.4%. The recent growth rate is faster than the population AGR of 2.16%--but only barely. Just because one population is growing faster than another doesn't mean it will catch up any time soon. (This is also an important principle to keep in mind when you're thinking about scary stories of the "Islamization" of _x_, where _x_ can be any place in the world.) Let's look at this growth rate charted for Thailand:
The size of the church is very small: just 850,000. Remember "percent" means "per hundred." Every year, the global population is adding 216 people "per hundred" - but there are many more "hundreds" in 65 million people (the total population) than there are in 850,000. If the current growth rate is maintained, the two bars won't cross any time soon.
So, are the Thai "reached"? Is the task finished? If you define the task as planting a church that can reach the whole of the group, then the answer is yes: given the right strategy and enough time, this church could reach 65 million. If the task is a church that "will" reach the whole of the group, a church with the vision, resources, scalable strategy, etc., within a specific time frame (say one or two generations), this chart clearly says--no, the task is not finishable. Now, it is true that what appears to be unfinishable now might actually be finishable later if you are using an exponential growth strategy. Look at this chart as an example:
The bottom left section ("Looks like it won't be finished") looks remarkably similar in some ways to the Christian portion of Thailand in the chart above. And exponential growth looks like this: it goes and goes and goes and then suddenly achieves "lift off." It begins to "scale up." And then the task is rapidly finished. But this idea relies upon the kind of church growth strategy being used. To ascertain whether the task is finishable using this approach, we must assess whether the current strategy has the capacity of exponential growth, and how far it can scale. Can it reasonably scale to 100% of the population? What are the barriers along the way? If it can't scale, the task is not finishable.
We can measure this by asking what kind of growth rate would be required to "finish the task" (reach everybody) within a give time frame, and asking whether the strategy can achieve that level of growth. How to answer this for Thailand?
Here's 12% per year. This would do it by 2050--a growth rate 6x that of the overall population (and keep in mind these sorts of rates would also be needed for a small Muslim population, for example, to overtake a larger one).
I'm not saying this is easy. All I'm saying is this: in many places, the good that now being done will not get Christianity to the end goal. It will only preserve the status quo in which the church remains stagnant at 33% of the global population (as it has for the last 100 years).
I think before we count a group as "reached" or the task "finished," we have to ask this question (which I posed another way in Jesus wants the whole pie): will the task be finished all the way?
The Whole Church may have very well finished the "engagement" part of the task. The Church may even have finished the "plant a church" part of the task. But if the way these tasks have been finished prevents the future tasks from being finished all the way--are we really finished? Have we done our part?
If a church has been planted, but planted in such a way that it does not have the capacity, will, resources, strategies, whatever, to actually reach the population (and this is evidenced in the results it is presently achieving and markers that it will scale up), then... is the population segment (of whatever form) reached? It may seem like I'm picking on the Thai. This is just one example. You could pick lots of other places and find exactly the same problem. This is why movements, and engaging lots of places, is so important to me.