Consider a church of initially 60 people, where 5 new people come each year - the demand rate. In addition 5% of the church leave each year.
The church grows over the following 50 years, figure 1, but growth slows and exponentially tends to a limit of 100. The limit is independent of the initial size of the church. A church starting with 40 will reach the same limit, but would take longer to do so.
Church Growth Limited by Lack of Supply
Results of the Constant Demand Model
A church which does no work to supply the demand for religion from society is at the mercy of the demand rate. On average that demand will be constant in a stationary society. Church growth reaches a barrier determined by that demand rate and its losses. Demand may be increased if the church does work to supply the religious needs of society.
The growth of the church slows because as it gets larger, the number of people who leave is larger. The number who leave the church rises to match the number who come, figure 2. It will stop growing at 100 people because 5% of a 100 is 5; the outflow matches the inflow!
The limit of the church is also set by the leaving rate. The balance of demand rate and leaving rate determines the ultimate church size.
If a church size starts over the limit, then its numbers will exponentially decline to the limit. With the same demand and leaving rates as above, consider a church initially at 150. After 50 years the church has dropped to near 100, figure 3.
If a church starts in equilibrium and the demand varies, then the church numbers will track the demand but delayed in time. Figure 4 shows a variable demand rate (curve 2). The church size increases and reaches its peak around 10 years or so after the peak in demand. As demand falls, the church declines. Note the church numbers are smoother than the demand as they are the accumulated number in church, most of whom remain for many years.
Church still survives even after demand has ceased, but heads for extinction. The lesson here is that the warning sign for the church was its fall in recruitment, not its decline in numbers. Churches need to monitor inflows and outflows, as well as total number. Action needs to be taken when recruitment declines, whether that is people joining or conversions. By the time demand is low it may be too late to reverse decline as much of the loss rate is due to deaths, which cannot be avoided.
Additionally, a church that does no work to create demand for its religion cannot expect to survive.
This model suggests two strategies that raise the limit the church numbers reach.
1. Reduce Losses
Using a demand rate of 5 people coming to church each year, and a loss rate of 5% per year. Consider reducing the loss rate after 25 years to 4.5% (curve 2, figure 5) and 4% (curve 3), comparing the result with no reduction in losses (curve 1). In each case the limit is raised by a small amount, leading to a larger church in time. However as some of the loss rate will be deaths, which cannot be reduced, a change of a half percent or one percentage point in losses may be too hard to achieve. This is especially true in an elderly church where deaths are the main part of the losses.
2. Increase Demand
The same graphs in figure 5 can be achieved by increasing the demand rate to 5.5 per year (curve 2), and 6 per year (curve 3). It can be argued that increasing the inflow rate is easier to achieve. Better worship services, pastoral care, could attract people on the margins of church. Advertising could increase the pool of people who are aware of the church, thus increasing demand. The key to removing this limit to growth is to increase demand.
The church in this model is providing no supply to meet demand, or doing no work to create demand. To remove the growth barrier it must link the size of the church to measures to increase the inflow. The principle should be: the bigger the church, the bigger the effort in recruitment, by whatever means. More people in the community will be met, thus greater sharing of the gospel, more persuasion. Churches must not take demand for religion for granted, but should take actions, the supply, to capitalise on the demand and increase it.
From a system dynamics point of view the balancing feedback loop B needs opposing, SD model figure 1. Somehow a form of feedback that reinforces growth must be introduced. These strategies are examined in the Supply and Demand Model, and the Limited Enthusiasm Model.