Southern Baptist Convention USA 1980-2012
Application of the Limited Enthusiasm Model with Demographics
Membership data for the Southern Baptist Convention (SBC) in the USA from 1980 to 2012 was fitted to the Limited Enthusiasm Model of Church Growth. It was found that the although the denomination had been growing up to the 21st century in revival growth mode, since 2006 it has declined in a way inconsistent with its previous growth. That is the decline cannot be described as a natural consequence of its prior growth, such as the overshoot phenomena that can happen with revival growth. At least one of the parameters must have changed since 2006 in order for the data to fit the model. Either enthusiasts are less effective, with less conversions; or people are leaving in greater numbers, perhaps to other types of churches; or society is becoming increasingly hardened to the SBC. Although birth rates are falling, this is not sufficiently fast enough to explain the drop in membership as a cohort effect alone.
Membership figures for the SBC from 2004 were obtained from the Southern Baptist Annual Reports. Earlier figures were obtained from adherents.com who use a variety of published sources. From 1950 membership has increased until 2006, although that increase had been slowing since mid 1980s (figure 1). Since 2006 the membership has declined sharply.
Figure 1: SBC Membership 1950-2012
Given people attend church for some time before joining, and stay on membership roles for some time after they stop attending, the membership figures probably reflect an attendance pattern of a few years earlier.
USA population data was obtained from the US Census. As a fraction of the total population the SBC peaked in the 1980s (figure 2). Since then it has not kept pace with demographic changes. The falling birth rate would work against it, whereas the rising immigration rate is unlikely to help as immigrants may not be a large source of recruitment for most SBC churches who lie outside of big cities.
Figure 2: SBC Membership as Percentage of USA Population 1950-2012
The data was compared with the General Limited Enthusiasm Model, which assumes growth is driven by a subclass of church members, called enthusiasts, who eventually lose their potential to reproduce themselves through the conversion of unbelievers. Data was fitted from 1980 to prevent earlier trends dominating over later ones. Some of the changes from earlier decades may reflect societal changes not in the model. Data fitting was stopped in 2006 so that the model's membership predictions for subsequent years could be compared with what actually happened
A best fit between model and data gives a value for the reproduction potential and the two thresholds of extinction and revival growth. Many such "best fits" were obtained for a variety of initial values of enthusiasts and hardened unbelievers, as their values cannot be measured. From that range of "best fits" the distance between each threshold and the reproduction potential was examined.
Other parameters are determined as follows:
All the best fits show the church well above the extinction threshold and above the revival-growth threshold for at least the 1980s. However most best fits show that revival growth had stopped by the first decade of the 21st century. Subsequent behaviour shows the growth of the church slowing leading to a small decline due to overshoot. The church membership numbers would eventually settle to an equilibrium value, but on a timescale much longer than the validity of the parameters, and the simulation. Thus the growth of the SBC was expected to come to an end by 2006 which confirms a similar result in A General Model of Church Growth and Decline.
A pessimistic data fit, where the SBC ceased revival growth in 1990, can be compared with an optimistic fit, where it only just ceases revival growth in 2006. Figure 3 compares two such fits with the data. There is little to choose between the two scenarios on the basis of the data from 1980 to 2006. However extrapolating from 2006 onwards the optimistic scenario shows growth continuing, due more to demographics than revival growth. The pessimistic fit shows the decline due to the overshoot caused by the earlier growth, an effect due to people continuing to leave the church in large numbers when growth has slowed. Even the pessimistic fit is well above the actual data.
Comparing the data with the pessimistic fit (figure 3) it can be seen that the actual decline in membership after 2006 is much faster than the rise before 2006. The data is not symmetrical, which implies another effect has been increasingly important from 2006 that is causing the decline. The variations in birth and death rates are already built in to the model, and they do not change fast enough to account for such a decline. Including immigration would only make the difference between the data and the model greater.
Three explanations are suggested:
The decline could be a combination of all three effects.
If the reproduction potential continues to drop at the rate suggested by the recent data then the effect on the SBC membership figures will be dramatic (curve 2. figure 4). The church will drop to under 12 million by 2025, well below its 1980 figure. If the cause is rising leaving rate (curve 1, figure 4), or an increasing hardening rate of potential converts (curve 3, figure 4) the decline is likewise dramatic. Thus if the SBC is not to see serious decline, the source of its drop in membership figures needs to be identified and dealt with.
Figure 5 compares the reproduction potential (line 3) with the extinction threshold (line 2) and revival growth threshold (curve 1), for the pessimistic scenario. The revival growth threshold rises as the number of potential converts fails to keep pace with demographics, due to conversion, and due to people becoming hardened to the Christian message. After 1995 the reproduction potential is under the revival growth threshold and growth then slows to a halt. Up to 2006 the reproduction potential is well over the extinction threshold (line 2).
Figure 5: Reproduction Potential compared with Extinction and Revival Growth Thresholds
If the parameters do not change then stability would be achieved with revival growth threshold matching the reproduction potential. However the data from 2006 suggest one or more parameters have changed.
The timescales of these events are way beyond the end of 21st century, outside the time horizon of the model, but it gives a flavour of the seriousness of the decline.
Figure 6: Reproduction Potential & Thresholds, Increasing Leaving Rate Scenario
Figure 7: Reproduction Potential & Thresholds, Decreasing Reproduction Potential Scenario
Figure 8: Reproduction Potential & Thresholds, Increasing Hardening Rate of Society Scenario
There are a number of conditions that must be applied to this result.