One of the most remarkable graphs I have ever seen was developed by ANSR’s own Rich Houseal. While he was serving as president of ASARB he was able to acquire, from five other denominational statisticians, the church attendance data for their respective churches. Attendance data has only been collected in recent years and has not been readily available. Of course, actual report data is more desirable than survey data. It may not be 100% accurate but it is generally consistent and reliable. Most denominations have standard reporting procedures which over time have produced an acceptable level of reliability.
Sullivan, B. M. (2008). Understanding Church Size Based on Empirical Data. Journal of the American Society for Church Growth, 19(1), 13-22. Retrieved from https://digitalarchives.apu.edu/jascg/vol19/iss1/3