Conversion Research: The Future of Church Growth Research

by Marten Visser

A conversion research project on the growth of the Thai Protestant Church addressed what kind of people become Christians and what types of churches attract non-believers.

Church growth research has changed into a slightly disreputable branch of missiology. Originally, it focused on the growth of God’s Church in non-Christian settings. The American incarnation of the discipline quickly shifted its focus to the growth of “my church” (cf. Wagner 1984). Although there certainly is a place for that kind of thinking, three important disadvantages were often connected to this new approach. First, church growth evolved into marketing, and biblically-sound theology was put on the back-burner if it was perceived as hindering the quick growth of the church. Churches turned their Jesus into a more palatable, less demanding god, and in the process lost their voice of calling people to repentance and faith.

Second, the emphasis of growing “my church” without much reflection upon where the members are coming from contributed to the “recycling of the saints” without growth of God’s kingdom. Third, putting up the megachurches as examples for others to aspire to resulted in a lack of recognition for the strategic value of church multiplication (even though some of the megachurches are also exemplary in planting daughter churches). As a consequence, church growth research fell out of favor in a large part of the missiological world. Yet there is no reason why this should be so.

If it is true that Jesus Christ is the hope of this world, and if it is true that church membership is an indicator (not a sufficient, but yet a necessary, indicator) of a connection with him, church growth research remains important. What kind of people become Christians? What kinds of churches attract non-believers? The answers to these questions may help inform policy decisions by churches and missionary organizations. For research to be acceptable to Christian leaders, the above mentioned tendencies need to be addressed. I believe that a conversion research project on the growth of the Thai Protestant Church did just that.

Thai Research Project
In the Thai research project, all four thousand Thai Protestant churches were approached with questions about membership and attendance, so that a reliable count of Thai Protestants was achieved. It was found that only 0.5% of Thailand’s population are affiliated Protestant Christians, which is lower than the numbers given by Operation World and the World Christian Encyclopedia (Visser 2008, 77). Yet the news is not all bad. Protestants are growing four percent faster than the population. This means that Thai Protestantism is on the same growth curve as the Church in the first three centuries AD. Christianity grew from a small group in Israel to the large majority in the Roman Empire.

If the Thai Church keeps growing at the present rate and the Lord tarries, Thailand will be fully Christian in 135 years. However, not satisfied with just counting, I wanted to gain deeper insight into the composition and growth of the ethnic Thai Church. In a random sample of ninety-four ethnic Thai churches, all worshippers were asked to fill in a one-page questionnaire. Instead of looking at just local church growth, the research focused on conversion church growth. A conversion growth rate for each church was calculated based upon the percentage of respondents who had become Christians in that church within the last decade. After analyzing the data from ninety-four churches and over three thousand respondents from throughout Thailand (and from all kinds of Protestant traditions), I was able to give clear answers to the questions, “What kind of people become Christians?” and “What kind of churches attract non-believers?”

What Kind of People Become Christians?
In the mission world, there are some popular ideas about who is receptive to the gospel. Some of these ideas prove to be true; others totally erroneous. As is true in many parts of the world, in Thailand traditional religionists are far more receptive to the gospel than adherents of the majority religion (Buddhism in Thailand). Women are more receptive than men, migrants more receptive than non-migrants, and students more receptive than non-students. In none of these cases, however, was the less receptive group more than two times less likely to become Christian.

So although some real differences in receptivity were found, nowhere was there either a mass movement toward Christ or total resistance. Contrary to conventional wisdom, in Thailand youth are not more receptive to the gospel than older people. People over sixty are even twice as likely to become Christians as youth between the ages of fifteen and nineteen. Other findings were more ambivalent. In Thailand, urbanites and highly-educated people are more likely to become Christians than rural and lower-educated people. However, there was no indication that they were more receptive to the gospel. Likely, the reason for this pattern is that churches and missionary organizations focus on reaching highly-educated urbanites more than lower-educated rural people.

Several other interesting findings all point toward the paramount importance of personal relationships in the conversion process. Probably the most staggering statistic from the project is that a Thai with a Christian relative is seven hundred times (!) more likely to become a Christian than a Thai without a Christian relative. This has to do with opportunity. Many Thai people who do not have a Christian relative have never had the chance to respond to the gospel. Yet more than anything else, it shows that the gospel travels along relational (above all family) lines. The same conclusion can be drawn from the fact that seventy percent of all converts say that a lay church member (not a pastor or missionary) was the main influence in their conversion. Because of a popular formalized “accepting Jesus” ceremony normally led by a pastor, the real number is probably even higher.

Another finding that stresses the importance of social networks in conversion is that people in a village with a church are one hundred times more likely to become Christians than people in a village without a church. The very committed are willing to travel to church. But for the large majority of the population, Christianity only becomes an option when there is a church within their community. This gives strong support to the goal of saturation church planting.

A final “nugget” from the data reinforcing the importance of personal relationships was a surprise to the researchers. Limited to one choice, sixty percent of all converts claimed that print media had played a role in their conversion, while only ten percent mentioned non-print media (thirty percent said media did not have any influence). The likely explanation for this phenomenon is that radio and television are broadcast media, but print media are used in personal relationships. Even the oft-maligned tracts were mentioned almost twice as often as radio and television combined!

What Kind of Churches Attract Non-believers?
The discussion about what kind of churches grow through conversion can be an emotional one, and is often done without a lot of factual information. For this research project, fifty nine claims were analyzed statistically. Fourteen were clearly correlated with conversion growth. When these fourteen variables were entered into a mathematical model, only four were left that together predict over ninety percent of the conversion growth of an ethnic Thai church.

Two major factors explain more clearly what you need to know about the conversion growth potential of a Thai church. The first one is the age of a church. Age predicts about sixty percent of the conversion growth. Younger churches attract many more converts than older churches (e.g., a 5-year-old church attracts six times more converts than a 75-year-old church, all other things being equal). The second important factor is traditionalism. Churches with a lot of extra-biblical rules and an emphasis on position instead of spiritual giftedness are growing much slower than non-traditional churches. Traditionalism predicts another twenty percent of the conversion growth of a church. Two minor factors add some extra understanding. Eight percent of conversion growth is predicted by whether or not a church is charismatic (charismatic churches grow faster), and five percent by whether there are women on the church board (churches without women on the board grow faster). While the two minor factors are theological questions that should be decided on their own merits and not on the question of effectiveness, the two main factors should be theologically uncontroversial. Therefore, they clearly point to a ministry direction. God is using many churches, new churches, and churches that do not limit member ministry by emphasizing church rules and church positions to build his kingdom in Thailand.

Why This Is Important

Hopefully by now it has become clear that conversion research is a useful tool to analyze the state of a national or regional Church. Because it focuses on conversions rather than membership growth, a church that plants daughter churches is as likely to have a high conversion growth rate as a megachurch that incorporates everybody into one church. Taking the network of daughter churches into account as well, the conversion growth rate is likely to be even higher, because of the higher growth rate of younger churches. Getting your growth from the membership of other churches is not going to result in a higher conversion growth rate. So the conversion growth rate used in this research project is a better measure of a church’s contribution to the advance of the Christian faith than traditional church growth measures. In most cases, the analysis will point out practices that facilitate conversions and practices that build barriers against conversion. Conversion research is also likely to pinpoint receptive segments of the population, or, equally important, show that segments perceived as receptive are not more receptive, but only more heavily targeted than other groups. Again, this analysis likely results in common-sense ministry recommendations.

How You Can Do This Too
This article is written with the hope that in many more countries and regions research like this will be done to serve God’s Church. I am aware that few missionaries are equipped to do the advanced analyses used in the research project described here. However, there are several resources available that make conversion research doable for missionaries with a research interest but minimal statistical training.

1. A full description of the research process and findings can be found in Marten Visser’s Conversion Growth of Protestant Churches in Thailand.

2. I am happy to provide a CD-ROM with example forms and questionnaire, a check-list for conversion research projects, and an example data set from the Thai research project.

3. I am available for consultation on new conversion research projects.

4. Turnkey statistical analyses are being worked on. When they are ready, the researcher needs only to key in the data, and the analyses will be performed automatically.

I hope and expect that conversion research will bring new life to the use of statistics in missiology, and that it will help God’s Church in many countries to understand what is going on, and how the churches may best use the opportunities God gives them.


Visser, Marten. 2008. Conversion Growth of Protestant Churches in Thailand. Zoetermeer: Uitgeverij Boekencentrum.

Wagner, C. Peter. 1984. Leading Your Church to Growth. Ventura, Calif.: Regal Books.


Marten Visser is a church planter and OMF regional leader for Isaan (Northeast Thailand). He earned his Ph.D. in missiology from Utrecht University, studying conversion growth of Protestant churches in Thailand.

EMQ, Vol. 46, No. 2, pp. 200-204. Copyright  © 2010 Evangelism and Missions Information Service (EMIS).  All rights reserved. Not to be reproduced or copied in any form without written permission from EMIS. 


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