In my last blog, Closing Rural Churches , I said that no strategy to reverse church decline would work unless it deals with the root cause of decline, the church’s failure to recruit sufficient people to counteract its losses. In this post I will put forward evidence that lack of conversions is the primary cause of church decline in the UK since the end of the 19th century.
I will investigate this hypothesis by looking at data for the Presbyterian Church of Wales, (aka the Calvinist Methodists), one of the few denominations to record conversions, the children of members who join, transfers within the church, leavers and deaths. This data set was reproduced by Currie et al for 1895-1968 .
First Church Decline Hypothesis 
Church Decline is Caused by Lack of Conversions
Stated more specifically, the fall in membership across most of the pre-1900 denominations is due to their inability to keep conversion at the level of the 19th century. The Presbyterian Church of Wales is typical of this decline, as shown in the membership figures for the whole church , figure 1.
The church started in the mid 1730s and had risen fast in the early part of the 19th century. That rapid rise continued until 1905, the end of the last national revival in Wales, and has declined since.
To show that lack of conversions is the primary cause of this decline, compare the different growth and loss rates for 1896-1900 with 1964-1968, figure 2. Growth comes from two sources: the children of church members becoming members themselves once they have reached adulthood, called biological growth; and conversions, the people who join from outside the church. The losses also have two sources: deaths of members; and reversion, the total of those who resign membership, those expelled, and the discrepancy in the transfers between different congregations of the denomination .
At the end of the 19th century the conversion rate of 1.20% was higher than the reversion rate of 1.12%. However by the 1960s the conversion rate has dropped to a mere 0.4%, with reversion at 1.74%. The dramatic drop in the number of conversions is a significant factor in the change from growth to decline of the church.
A second cause of decline is the drop in biological growth, the children of members. This drop is smaller than that of conversions, and is in line with the general decline of the national birth rate from 2.86% in the late 1800s to 1.61% in the 1960s. Remarkably the child retention rate has improved from 51% to 60%. Thus though the national drop in birth rate has contributed to church decline, the church’s ability to keep its own children is not a contributory factor.
The third cause of decline is the rising death rate. In the 1890s the death rate of the church, 0.83%, is less that the national death rate of 1.7%, suggesting the church at that time was significantly younger than the population. By the 1960s the church death rate has risen to 1.68% much higher than the national death 1.18%, indicating an older than average church. Thus aging is a factor in the church’s decline.
So why has the church aged? Some if it is obviously demographic, falling birth rate. However the church has aged more than society, and was significantly younger than society at the end of the 19th century. I suggest that this relative youthfulness was due to the higher conversion rate, as conversions generally occur when people are younger. By the same reasoning the lack of conversions in the twentieth century has caused the church to age faster than society.
Thus whether directly, or indirectly through aging, lack of conversion is the root cause of the Presbyterian Church’s decline.
Let me investigate some alternative explanations.
Was Child Retention a Cause of Church Decline?
As already stated, the church’s child retention rate in the 1960s was better than it had been at the end of the 19th century. Figure 3 shows that the child retention rate has generally improved slightly from 1895 to the late 1950s. Its fall in the early 1960s is neither large nor systematic.
Though it has been common to blame the church’s inability to keep their children as a cause of its decline, figure 3 clearly shows this is not the case. Of course the birth rate has fallen during this time, and that may have led churches to think that their older profile reflected their lack of attraction to the young. However, in common with the rest of society, they were not producing children in sufficient numbers to keep themselves young . Child retention remained good and was not a cause of decline.
Were Emigration and War Causes of Church Decline?
The changes in the sources of growth and decline can be tracked from 1896 to 1968. Figure 4 shows falling biological growth together with the rising death rate of the church; the former due to falling national birth rates. The gap between these represents the aging profile of the church. Ignoring the temporary rise in deaths during the First World War, the aging process really starts in the 1920s. Some of this would be due to emigration between the wars as seen in the population figures for Wales. But as the narrowing of the gap with the biological growth continues, and then becomes negative as deaths exceed child retention, emigration cannot be the sole cause .
Likewise the effects of war are confined to 1914-1918 alone. The Second World War had little effect on the general trend of death rates, in fact they temporarily improved. Biological growth fell during this war, but only in line with the fall in birth rate 15 years previously. It rose again in the 1960s when the post war baby boomers became eligible for membership . Thus neither war had any ongoing impact on the church’s decline.
Was Church Decline Caused by a Higher Leaving Rate?
The conversion and reversion (leaving) rates are given in figure 5, with the very high conversion rates for the 1904-5 revival excluded . Before the revival the evidence is that conversion was just higher than reversion, though during the revival the conversion rate became massively higher, over 6%. After the revival reversion rises temporarily, although nothing like the level of the revival’s conversion rate.
The cause of the temporary rise in reversion may have been due new converts disillusioned with a church largely unaffected by the outpouring of the Spirit. Rather than abandoning Christianity the leavers formed independent mission churches and became part of the emerging Pentecostal movement, an offspring of the revival .
The only other significant change in reversion rate is during and after the Second World War. The lack of people leaving during the war is counter-balanced by a larger number leaving in1947-8, possibly a delayed effect due to people returning from the war.
Generally reversion has remained steady around 1.5% and has not contributed to the increasing decline of the church. Rather, as figure 4 makes clear, decline has come from the falling conversion rate.
What if the 1890's Conversion Rate Had Been Maintained?
The membership figures for the Welsh Presbyterian church can be adjusted assuming the pre 1904-5 revival conversion rates had been maintained. Comparing them with the actual membership figures shows that although the church would have still declined, it would have done so far more slowly, figure 6.
As such 58% of the church decline was due to the falling conversion rate, with most of the remainder due to the falling national birth rate and the aging of the church, the latter also partly due to lack of conversion.
Thus I conclude that lack of conversion is the root cause of the Presbyterian Church’s decline.
It is clear from figure 6 that maintaining the conversion rate would not have been sufficient to prevent decline. This is because even at the end of the 19th century the conversion rate was only just higher than the reversion rate; so that the church required high biological growth to help it keep growing, figure 2. There is a suggestion here that the late 1800s conversion rate was already inadequate for a church seeking to grow as a proportion of society.
Thus the 20th century decline, due to lack of conversions, was continuing a trend that had started even before 1895. The next blog will attempt to link this lack of conversions to the lack of revival in the church.
Although the study was just for the Welsh Presbyterian Church, nevertheless there is no reason to believe it is any different to the Methodist, Congregational, Anglican and Baptist churches, or those in Scotland and England, all of whom declined throughout the twentieth century.
I thus conclude that the primary cause of twentieth century church decline is the poor conversion rate.
Next blog: Church decline caused by lack of revival.
Notes and References
 Closing Rural Churches: Is this the Way to Church Growth?
 Currie, R., Gilbert, A. D., & Horsley, L. S. (1977). Churches and churchgoers: patterns of church growth in the British Isles since 1700. Oxford University Press, USA.
The data table is available from British Religion in Numbers
 In a subsequent blog I will illustrate a second church growth hypothesis that church growth is caused by revival. I will show that it is the lack of revival that lies behind the lack of conversions of the twentieth century onwards.
 The figures used are full members plus adherents, called the whole church by Currie et al. The Presbyterian Church of Wales had two classes of members. All could participate in most aspects of church life, but only the full members could attend the experience meeting, the seiat, seen as a high privilege.
Membership and adherent figures are known from 1860 (Williams, J., 1985. Digest of Welsh Historical Statistics. UK: Government Statistical Service HMSO.) However he does not record conversions, deaths etc.
From 1970 onwards membership data is taken from various publications by Brierley, see http://www.churchmodel.org.uk/growthrefs.html#stats As he only records full members not adherents the whole church is estimated by linearly interpolating from the shrinking gap between full membership and the whole church from 1950-1968 onwards.
 Most transfers were due to geographical mobility. For most years more people transfer out, compared with those who transfer in, presumably because people fail to take up their membership in the new church.
Conversions are called Probationers from Without by Currie et al.
Biological growth comes from Currie’s Children of the Church.
 It is highly likely that child retention has fallen since the 1960s. One estimate puts Christian child retention at around 30%, in contrast to the much higher rate among Muslims. See Intergenerational Transmission of Islam in England and Wales: Evidence from the Citizenship Survey, by J. Scourfield, C. Taylor, G. Moore, and S. Gilliat-Ray, Sociology, 46(1): 91-108, 2012.
 The loss of young men in the First World War, and emigration of largely younger people in the 1920s and 1930s, are often blamed as the cause of church decline. As the above analysis shows these are temporary effects. Each of these has could have three effects seen in: (a) falling church membership, (b) falling biological growth 15-20 years down the line, and (c) rising death rates well into the future.
(a) Although there is an increasing slope of decline in church membership from 1920, (figure 1), about the right time for an emigration effect, the leaving rate tells a different story. At the end of the 19th century the leaving rate averaged 1.1%, 3432 people per year. This increased from 1901-1904 to 1.21%, 4004 people per year. However from 1908, post revival to the start of World War One this increased dramatically to 1.46% 4961 people per year. From 1920-1935 the leaving rate then dropped to 1.45%, 4392 people per year; the still high percentage being due to a smaller church, rather than an increase in the number leaving, which had in fact dropped. Thus it is very difficult to prove that emigration had a large direct effect on church decline. The increasing rate of decline had started prior to the revival and was increased by the effects of the revival, both pre-war effects..
(b) Loss of young people in the war and through emigration would hit the birth rate during those times. The lowest birth rate is that of 1933 at 1.44%, compared with an average pre First World War birth rate of 2.5%. However the 1950s birth rate only recovers to an average of 1.6%. Birth rates were falling naturally apart from emigration and war effects. The biological growth of the church does fall from around 1.3% pre World War 2 to just over 1% in the 1940s and 1950, figure 4. Some of this is the ongoing effects of aging due to prior emigration and world war 1, but some will be due to aging through lack of conversions. The biological growth rate recovers briefly in early 1960s, but then has fallen further by 1968, suggesting an ongoing aging of the church, not just one due to fixed events such as emigration and war. As the church was only keeping 50% of its young people it must have conversions in order to stop aging as well as stopping decline.
 In the next blog, on the effect of revival on conversion and growth, these data points will then be included.
 For discussion of the disillusionment of revival converts see:
Jones, B.P. (1999). How Lovely are Thy Dwellings, Wellspring Books. Describes the beginnings of mission halls and Pentecostal assemblies after the 1904-5 revival.
Livesay, J. (2000). When We Walk with the Lord, published by the author, New Zealand, ISBN 0-473-06831-1. Describes the beginnings of the Apostolic Church, the Pentecostal Church that started in Wales after the revival.
Evans, E. (1969). The Welsh Revival of 1904. Evangelical Press of Wales.
Roberts, D.W. (2013). The Welsh Revival of 1904. What happened Next: Lessons from History. Available from Smashwords.