Three experiments are considered, namely the church’s response to:

  1. Sudden growth.
  2. Improving the Conversion Rate.
  3. Reducing the Conversion Rate.

Experiment 1 – Sudden Growth?

Let us start with a church of 90 people in equilibrium: 20 at basic discipleship, 30 early mature, 10 mature and 20 inactive. In addition, there are 10 potential converts attending the church, giving a stable congregation.

Normally, an average of 10 new people start church each year. This is balanced by losses and deaths, hence the equilibrium. Now in the second year let 50 new people start. In later years this drops back to 10. We could imagine that a year-long evangelistic campaign had taken place. How do the numbers in church change?

The immediate thought is with 40 extra people added in year 1 the church grows by 40. However, this is not the case! Figure 1 shows a sharp rise in the congregation size. Nevertheless, because the conversions are spread throughout the year, some of the early converts have already rejected the church and left before the later ones arrived. Thus, the congregation peaks at 127 people rather than the 130 we might have expected (Table 1). The church, i.e. all the converted Christians, takes longer to rise as conversion is not immediate. It peaks after 4.7 years at 106, 16 people above the 90 it would have been without the addition. Because the additions do not continue after year 2, the congregation and church are higher than they would have been, even after 20 years, but they are slowly settling back to the equilibrium position, as expected by the limited principle already established. The evangelistic campaign has increased church, but not as much as expected, and it has not given sustained growth.

Figure 1
Table 1

Note the sudden increase has made little difference in the growth in maturity of the church. There is a moderate rise in the basic disciples (curve 2 Figure 2), but later categories are reduced and delayed. The early mature, the spiritual foot soldiers of the church, have only risen by 7, and it has taken 8 years to reach this peak (Table 2). The mature only rise by 1 and peak (if we can call it that!) after 20 years.

Figure 2
Table 2

The delays are inevitable, regardless of how we define the categories, as maturity can be generated quickly. The lower increases are inevitable because there are always people who choose not to progress, backslide and even drop out of the church at any stage. It is clear that if we want growth in maturity, not just numbers, it is not sufficient to just have evangelistic campaigns, we must give attention to improving the discipleship process.

Experiment 2 – Improving Conversion Rate

Real church growth can only be achieved if there is an increase in the conversion rate or an increase in the attendance rate. Although conversion is a work of God and not under human control, there are probably many things we do that turn potential converts away from our churches (even if they are subsequently converted elsewhere). Thus we do have some control over the conversion rate into our individual church. Perhaps if we treated the potential converts better rather than ignore them, or gave them more user-friendly services rather than ones only meaningful to the deeply initiated. Figure 3 and Table 3 show the effects of increasing the conversion rate without any increase in the attendance rate that has fed this.

Figure 2
Table 2

The fraction who say yes (i.e. converted) increases from 0.449, the calibrated value for equilibrium, through 0.5 to 0.7. The results show a significant increase in church for higher conversion rates, although only over a long period. The short-term changes are quite small. The conclusion is that increasing conversion rates needs to be seen as a long-term solution to church growth and must be sustainable. That is any policy must be one that can be resourced for at least a generation. This should warn us against short-term fixes that take up so much of our time and energy that we cannot sustain them.

Experiment 3 – Reducing Conversion Rate

Sadly, conversion rates can drop. This may be due to our actions, for example, the need to divert our attention to urgent matters of church building repairs, thus spending less time with potential converts. Perhaps the drop in conversion rate may be due to changes in the type of people who attend, for example, the moral beliefs of people may have evolved away from those of the church, making the Christian message less attractive to them. Figure 4 and Table 4 show the effect of reducing the conversion rate from the calibrated value of 0.449 down to 0.

Figure 4
Table 4

Small changes only give a moderate decline. E.g. if only 30% of potential converts say yes to Christianity and stay in church, then church only drops to 70 after 20 years. Sadly this is not a sharp enough decline to prompt us into action. The zero conversion rate has a much steeper decline, but in churches like this, the leaving rate is often far less than the value used in the calibrated model. Thus the decline is much slower because it is through deaths alone.

One effect of a declining conversion rate is to alter the balance of maturity in the church. Figure 5 compares the balance of maturity of the church calibrated to equilibrium at 90, with how it would look after 20 years if it had a lower conversion rate. The inactive are the greatest category by far, and few people are being discipled. Although the percentage of the church mature has increased, this only happens because there are too few to disciple!

Figure 5

Former mature and early mature people have become inactive, that is they no longer either enable discipleship to happen nor are they interested in progressing in discipleship themselves. They are inactive in production and progression in discipleship. Neither are they involved in the spiritual activities of the church, other than attendance at worship. This is an inevitable result of decline and would, of course, accelerate that decline. Perhaps we should conclude that there should never be any retirement from active service for Christians and that discipling others and our own spiritual progress are an essential part of our Christian life.