Church growth models are divided into 4 families:
- Limited Enthusiasm: Conversion driven by enthusiasts, a subset of the church who do not remain enthusiastic indefinitely. Models based on epidemiology, population modelling and sociophysics.
- Congregational: Models of an individual congregation. The church congregation is divided into stages of disciples with differing roles in church life and recruitment. Mechanical pragmatic models.
- Limits-to-Church-Growth: Story-telling models that explore limits to the growth of the church. Hypotheses are general metaphors rather than operational or sociological ones.
- Sociological Models: Hypotheses from the sociology of religion, organisational theory, or other similar academic disciplines.
Limited Enthusiasm Model
Enthusiasts are the subset of the church who are active in converting unbelievers. They are “infected” with religion and pass it on to their friends, family and contacts. The result is that religion spreads like a disease, and the church grows. Growth ceases because enthusiasts lose their infectious enthusiasm and are thus unable to convert people fast enough from the shrinking pool of unbelievers. These hypotheses can be expressed in the system dynamics diagram:
There are three categories of people: unbelievers, enthusiasts (or active believers) and inactive believers. These correspond to the susceptible, infected and removed categories in the spread of disease.
In the basic model, new converts are the primary source of enthusiasts because they have the most contact with unbelievers. Extended models include births as a source of believers (Demographics Model), existing believers as a source of enthusiasts (Renewal Model), and the work of the Holy Spirit in conversion (Spiritual Life Model).
Congregational: Discipleship Model
The focus of this model is growth into maturity of Christians and its impact on the ability of the congregation to convert new believers and train them. There are two categories of non-Christians: Unbelievers and Potential Converts. The latter attend church in varying degrees. There are four categories of believers, representing training, what they require of the church, and participation, what they give to the church. Each stage flows into the next:
At any stage, believers may stop progressing, become inactive, or leave. The model explores the difficulty of maintaining a balanced, healthy church.
However fast church congregations grow, there comes a point where growth slows and eventually stops. What has limited its growth? Many suggestions are made: lack of physical resources, human resources stretched too much, complacency, inability to organise for size, and lack of demand (as below).
Models are constructed to illustrate the different barriers to growth and how they may be tackled.
These implement sociological hypotheses that explain church growth and decline. For example, the institutional lifecycle from organisational theory is based on the hypothesis that attempts to build the organisation (R1) are undermined by its growing institutional needs (B2). Once decline sets in (B1), institutional structures do not decline fast enough for growth to return and future extinction results. The figure below applies these hypotheses to a church denomination.