Stella 9.1 model can be downloaded from http://forio.com/simulate/jhayward/limenthmig/model/download/?hard=true.
Model author: John Hayward, Church Growth Modelling.
The model that loads is of revival growth taking placed in a population that is growing through migration. All the migrants are unbelievers. There is an initial burst of rapid growth followed by repeated bursts of revival growth due to the pool of susceptible unbelievers continuing to increase and tipping the church over the revival growth threshold.
Change the number of immigrant enthusiasts to 25 per year and there are no repeated bursts of revival growth just the initial one, followed by steady growth and an endemic state of enthusiasts. See the migration results page for details.
Migration Model Simulation
The central hypothesis of the limited enthusiasm model is that conversion growth in the church is driven by a sub-group of church members called enthusiasts. The model is extended to include migration of people into the catchment area of the church, where its value is determined by outside factors.
The simulation is embedded below, or can be opened in a separate window: http://forio.com/simulate/jhayward/limenthmig.