In school, we typically learn addition then subtraction followed by multiplication and division. In spiritual life, I would argue it's more important to learn multiplication first, then addition, and avoid division and subtraction altogether. My small group experience has been that when we learn small group addition first and then sometime much later try to teach multiplication, it many times leads to division and subtraction!
Let me explain what I mean by defining some terms. First, let's define small group "multiplication." For this discussion, I'll define small group multiplication as the process of reproducing Biblical values, knowledge, experiences and skills through a relational and experiential process. But not only are the values, knowledge and skills to be reproduced in another, the very reproduction process is to be also passed on repeatedly from one small group leader to another emerging small group leader and in turn from one small group to a new small group. In essence, multiplication's root goal is seeing growth through a complete replication of the existing leader and group.
On the other hand, I'll define "addition" as the process of assimilating new members and selecting new leaders through any process that doesn't have a primary expectation that Biblical values, knowledge and skills will be reproduced repeatedly in another leader/group through modeling and relationship. In essence, addition's root goal is seeing growth through adding another leader or group to the existing system without disturbing pre-existing small groups.
Obviously, addition and multiplication are both Biblical values (see below). Both need to be happening in ministry. But, how people are taught to do them is very important. In the laboratory ...