If one out of every ten groups in a movement plant a new group each year, the number of groups (and adherents, roughly) will double every 10 years.

If one out of every three groups in a movement plant a new group each year, then doubling will occur about once every three years.

If one out of every two, then every other year.

The reason many traditional churches don’t see movement style growth is simply that they don’t do the things necessary to plant and teach others to do the same thing. They do things that are lead to church growth – that is, the growth of the individual church. (Invitation, attraction, etc. to a central location.) They may be very good (or perhaps middling, or very bad) at growing the numbers of the congregation up to a local maximum–but never surpass the local maximum because they don’t do the sorts of (messy) things (outreach, dealing with messy people, planting new churches) that would allow them to massively surpass the individual congregation.