You asked for the source?
The World Christian Encyclopedia (David A. Barrett; Oxford University Press, 1982) apparently estimated almost 21,000 denominations, and the updated World Christian Encyclopedia (Barrett, Kurian, Johnson; Oxford Univ Press, 2nd edition, 2001) estimated at least 33,000. “Denomination†is defined as “an organised christian group within a countryâ€.
The Center for the Study of Global Christianity at Gordon-Conwell Theological Seminary estimated 34,000 denominations in 2000, rising to an estimated 43,000 in 2012. These numbers have exploded from 1,600 in the year 1900.
Thanks... (really)
I will try to digest some of these sources to see why the numbers are so unexpectedly high.
I promise to get back to you.
I did find this already (from your Gordon Conwell source):
World Christian Database700 is a believable number of evangelical denominations. I am in that group, btw.The World Christian Database (WCD) is an online resource based on the World Christian Encyclopedia (Oxford University Press, 1982, 2001) and World Christian Trends (William Carey Library, 2001). Data for the WCD are constantly gathered, analyzed, and updated by full-time staff at the Center for the Study of Global Christianity at Gordon-Conwell Theological Seminary (South Hamilton, MA, USA).
The WCD currently uses a "structural" approach in defining Evangelicals: Evangelicalism is a movement, primarily within Protestantism, consisting of all affiliated church members self-identifying as Evangelicals. Christians are also considered Evangelicals when they are members of an Evangelical church, congregation, or denomination. Characteristics of Evangelicals include personalized religion (including being "born again"), dependence on the Bible as the word of God, and regular preaching and/or evangelism. This structural approach leads the WCD to claim that there are 706 Evangelical denominations worldwide with a total of around 300 million adherents in 2010.
Again, I want to sincerely thank you for providing the sources.