I have been frequently asked, “what size counts as a movement” and “how fast does a movement grow”? The common definition I use for a movement is: “consistently reaching four generations of church planting in short periods of time.” Obviously, this leaves a little ambiguity: movements are not machines, made up of precisely engineered pieces of metal, but rather structures like forests, made up of organically growing groups of people.

This week, however, I heard a suggestion of size from a global movement coach that seemed to fit. He noted that it takes some time to get to four generations: often years. Once four generations is reached, “most movements” typically add another generation each year.

At first, this might sound as though it would take a long time to double: four generations, adding one generation per year, would take four years to double. However, we are not interested in the number of generations, but rather in the number of believers, groups, and churches. Disciples who make disciples leads to exponential growth; groups that multiply groups enhance this further. If each generation is larger than the last (and they will be, if church planting is done in multiple streams) equates to multiplying growth that takes up a larger percentage of a given population.

Let’s use some numbers to illustrate this. Assume a movement thatĀ is a precisely engineered machine (just for the sake of the illustration). Each group averages 14 people, and each group plants three new groups in a period of one year.

Growth is very slow at first: months can go by with no groups and perhaps no believers. The leap between year 3 and year 4 will be easily remarked upon; the leap between year 4 and 5 even more so. Between year 7 and year 8, the movement would become very difficult to track.

How fast things can change (and how difficult it can be to track) is readily obvious from just trying to chart such growth:

… only two strands instead of 3 off the original host, and only goes down 5 generations…

This is not just an abstract exercise. The original spreadsheet above has the appearance of an arm-chair theoretical exercise, but we now have dozens of case studies of movements, many of which are either somewhat faster or slightly slower than this growth curve.

Let’s do something different. What if the movement is a little messier? Let’s say that only 60% of the churches make another church. Those numbers would be:

This is a much slower growth pattern, obviously, but it would still significantly impact any single district of ~100,000 population, and be closing in on 1% of a million-population province. In some unreached areas, that would be a game changer.

The point: a movement doesn’t have to add another four generations in a single span of time (e.g. a year to two years); it needs only to add one. That is a huge triumph: adding another generation (e.g. each church in the furthest out generation plants 2 to 3 new house groups) each year would lead to massive doubling, and in one generation of people (~20 years) could change the course of a nation.