The model consists of one group of people: Church, measured by attendance or membership. There is no model of those outside church as demand is assumed potentially unlimited. In addition there is one variable Resource to represent one or more of the resources that enhance growth. Zero resource will mean no conversion/recruitment to the church is possible. The resource has a maximum capacity.
The dynamic hypotheses are:
|Church supplies religion in proportion to its resource (R).||The larger the resource the more people are recruited from outside the church. This may be achieved directly through contact with unbelievers, or indirectly via advertising, social networks, rumour on the street, or any combinations of methods. The resource generated by the church is instrumental in making any of the means of recruitment effective.|
|Church generates the resource in proportion to its size (R).||The larger the church, the more resource is generated. This may be because financial giving increases and thus more money can be used on staff, church buildings and advertising. There are more people to resource Sunday Schools, Bible studies, social programmes and other lay ministries. There are more people to encourage each other, engage in spiritual conversation and pray. There are more people to befriend and build social networks and capital.|
|People leave church at a constant proportional rate (B1).||This includes people giving up the church, and deaths. The reason people leave are personal, thus the rate is proportional to the church size, i.e. "per capita". Those who leave may rejoin as the source of recruits is potentially infinite.|
|The closer the resource gets to capacity, the harder it becomes to generate (B3). The "Brake".||When the resource is small it is relatively easy to generate. When the resource gets larger it becomes harder to generate, perhaps because of the organisational complexity involved. Staff and ministers may become individually less effective when working in groups. There may be a greater drop out rate in larger Sunday Schools and Bible classes because of the increased pastoral difficulties due to size. There is a capacity to the church building/worship area size affecting attendance and class provision. There is a capacity to the number of contacts and friends in social networks. There is a limit to what a person can receive of the spiritual life. Reputation and legitimacy effectively have a maximum. There is greater scope for strife and division undermining effectiveness. B3 acts as a brake on the resource.|
|If there is no resource generated, the remaining resource depletes at a constant rate (B2).||Organisations, networks, legitimacy and reputation deteriorate unless maintained. Staff naturally leave with a delay in replacement. People who service Sunday School and classes leave either the church, or no longer volunteer for that role. Spiritual life fades without input from the church.|
|Unlimited pool of unbelievers.||The size of society outside the church is infinite.|
Births are ignored but children born to church members can be assumed recruited with the same resource as those outside the church.
Unbelievers are added to the church according to the amount of resource (R). Church members leave at a constant rate per person (B1). The resource is generated according to the size of the church (R). The resource is harder to generate the larger it becomes (B3), measured next to its maximum resource (capacity). Resource depletes at a constant per capita rate (B2).
The leaving feedback loop B1 has a constant impact. However because loop B3 slows the generation of the resource, the reinforcing loop R has diminishing impact on recruitment. The limit to church growth is reached when the recruitment rate matches the leaving rate.
If the church subsequently declines because, for example, the leaving rate increases, then the smaller church will generate less resource as some of the existing resource will deplete in time, B2. A new lower equilibrium would be reached.